1. Introduction
1.1. Audience
Life with qmail is aimed at everyone interested in running qmail, from the rank amateur (newbie) who just installed Linux on a spare PC all the way up to the experienced system administrator or mail administrator. If you find it lacking or unclear, please let me know. Send comments to<EMAIL_ADDRESS>There's a wealth of information available on qmail from a variety of sources. Some is targeted to newbies, some assumes that the reader is more experienced. Life with qmail is an attempt to "glue" this information into a single source, filling in some of the cracks and assuming only that the reader has basic skills such as:
- Manipulating files/directories under UNIX
- Operating a web browser or FTP client
- Following directions
1.2. What is qmail?
qmail is an Internet Mail Transfer Agent (MTA) for UNIX-like operating systems. It's a drop-in replacement for the Sendmail system provided with UNIX operating systems. qmail uses the Simple Mail Transfer Protocol (SMTP) to exchange messages with MTA's on other systems.
Note: The name is "qmail", not "Qmail".
1.3. Why use qmail?
Your operating system included an MTA, probably Postfix or Sendmail, so if you're reading this document you're probably looking for something different. Some of the advantages of qmail over vendor-provided MTA's include:
1.3.1. Security
qmail was designed for high security. Sendmail has a long history of serious security problems. When Sendmail was written, the Net was a much friendlier place. Everyone knew everyone else, and there was little need to design and code for high security. Today's Internet is a much more hostile environment for network servers. Sendmail's author, Eric Allman, and the current maintainer, Claus Assman, have done a good job of tightening up the program, but nothing short of a redesign can achieve true security.
1.3.2. Performance
qmail parallelizes mail delivery, performing up to 20 deliveries simultaneously, by default.
1.3.3. Reliability
Once qmail accepts a message, it guarantees that it won't be lost. qmail also supports a new mailbox format that works reliably even over NFS without locking.
1.3.4. Simplicity
qmail is smaller than any other equivalently-featured MTA.
Note: The official qmail web page, http://cr.yp.to/qmail.html covers the advantages of qmail more extensively.
1.4. History
qmail was written by Dan Bernstein (DJB), http://en.wikipedia.org/wiki/Daniel_J._Bernstein, a math professor now at the University of Illinois in Chicago. Dr. Bernstein is also well known for his work in the field of cryptography and for his lawsuit against the U.S. government regarding the publishing of encryption source code. See http://en.wikipedia.org/wiki/Bernstein_v._United_States or http://cr.yp.to/export.html for information regarding the lawsuit.
The first public release of qmail, beta version 0.70, occurred on January, 24, 1996. The first gamma release, 0.90, was on August, 1, 1996.
Version 1.0, the first general release, was announced on February, 20, 1997. The current version, 1.03, was released on June, 15, 1998.
The next release is expected to be an evaluation version of 2.0. Some of things that might appear in version 2 are covered at http://cr.yp.to/qmail/future.html.
1.5. Features
The qmail web page, http://cr.yp.to/qmail.html, has a comprehensive list of qmail's features. This section is based heavily on that list.
1.5.1. Setup
- Automatic adaptation to your UNIX variant--no porting needed
- Automatic per-host configuration
- Quick installation--no big list of decisions to make
1.5.2. Security
- Clear separation between addresses, files, and programs
- Minimization of setuid code
- Minimization of root code
- Five-way trust partitioning--security in depth
- Optional logging of one-way message hashes, entire message contents, etc. (See What is QUEUE_EXTRA? in Appendix E.)
1.5.3. Message construction
- RFC 822 and RFC 1123 compliant
- Full support for address groups
- Automatic conversion of old-style address lists to RFC 822 format
- sendmail command for compatibility with current user agents
- Header line length limited only by memory
- Host masquerading (See defaulthost)
- User masquerading (See MAILUSER and MAILHOST)
- Automatic Mail-Followup-To creation (See QMAILMFTFILE)
1.5.4. SMTP service
- RFC 821, RFC 1123, RFC 1651, RFC 1652, and RFC 1854 compliant
- 8-bit clean
- RFC 931/1413/ident/TAP callback--can help track spammers/forgers
- Relay control--stops unauthorized relaying by outsiders
- No interference between relay control and aliases
- Automatic recognition of local IP addresses
- Per-buffer timeouts
- Hop counting
- Parallelism limit (via ucspi-tcp)
- Refusal of connections from known abusers (via ucspi-tcp)
- Relaying and message rewriting for authorized clients
- Optional RBL/ORBS support (via rblsmtpd)
1.5.5. Queue management
- Instant handling of messages added to queue
- Parallelism limits
- Split queue directory--no slowdown when queue gets big
- Quadratic retry schedule--old messages tried less often (see Appendix E)
- Independent message retry schedules
- Automatic safe queueing--no loss of mail if system crashes
- Automatic per-recipient checkpointing
- Automatic queue cleanups
- Queue viewing (See qmail-qread)
- Detailed delivery statistics (via qmailanalog)
1.5.6. Bounces
- QSBMF bounce messages--both machine-readable and human-readable
- HCMSSC support--language-independent RFC 1893 error codes
- Double bounces sent to postmaster
1.5.7. Routing by domain
- Any number of names for local host (See locals)
- Any number of virtual domains (See virtualdomains)
- Domain wildcards (See virtualdomains)
- Configurable "percent hack" support (See percenthack)
- UUCP hook
1.5.8. SMTP delivery
- RFC 821, RFC 974, and RFC 1123 compliant
- 8-bit clean
- Automatic downed host backoffs
- Artificial routing--smarthost, localnet, mailertable (See smtproutes)
- per-buffer timeouts
- Passive SMTP queue--perfect for SLIP/PPP (via serialmail)
- AutoTURN support (via serialmail)
1.5.9. Forwarding and mailing lists
- Sendmail .forward compatibility (via dot-forward)
- Hashed forwarding databases (via fastforward)
- Sendmail /etc/aliases compatibility (via fastforward)
- Address wildcards (See .qmail-default)
- Mailing list owners--automatically divert bounces and vacation messages
- VERPs--automatic recipient identification for mailing list bounces
- Delivered-To--automatic loop prevention, even across hosts
1.5.10. Local delivery
- User-controlled address hierarchy--fred controls fred-anything mbox delivery
- Reliable NFS delivery (See maildir)
- User-controlled program delivery: procmail etc. (See qmail-command)
- Optional new-mail notification (See qbiff)
- Optional NRUDT return receipts (See qreceipt)
- Conditional filtering (See condredirect and bouncesaying)
1.5.11. POP3 service
- RFC 1939 compliant
- UIDL support
- TOP support
- APOP hook
- modular password checking (via checkpassword)
1.6. Related packages
qmail follows the classic UNIX philosophy that each tool should perform a single, well-defined function, and complex functions should be built by connecting a series of simple tools into a "pipeline". The alternative is to build more and more complex tools that re-invent much of the functionality of the simpler tools.
It's not surprising, then, that qmail itself doesn't do everything everyone might want it to do. Here, then, are some of the most popular add-ons written for qmail. Of course, many standard UNIX utilities can also be plugged into qmail.
- dot-forward--a Sendmail .forward file compatibility add-on
- fastforward--a Sendmail alias database compatibility add-on
- ucspi-tcp--an inetd replacement
- daemontools--a set of tools for managing daemons and their logs
- qmailanalog--a set of qmail log file analysis tools
- serialmail--tools for mailing over slow networks
- mess822--tools for parsing Internet mail messages
- ezmlm--a mailing list manager for qmail
1.7. Architecture
Appendix D covers qmail's functional and physical structure. In a nutshell, qmail consists of a series of programs (modules) that perform different tasks.
1.8. License
As of 2007-11-30, qmail 1.03 is in the public domain. See http://cr.yp.to/qmail/dist.html. This means that there are no legal limits to what you can do with it: you can copy it, give it away, sell it, modify it, rename it, or use pieces of it in copy-protected works, without any restrictions.
Other packages by Dan Bernstein, such as daemontools and ucspi-tcp, are copyrighted by the author, and are not distributed with a statement of user's rights. In http://cr.yp.to/softwarelaw.html, he outlines what he thinks your rights are under U.S. copyright law. See also http://en.wikipedia.org/wiki/License-free_software.
1.9. Comparison with other MTA's
A book could be written about this topic, but it would be tedious reading. Here's a quick comparison of qmail with some of the most common UNIX MTA's.
| MTA | Maturity | Security | Features | Performance | Sendmailish | Modular |
| qmail | medium | high | high | high | addons | yes |
| Sendmail | high | low | high | low | x | no |
| Postfix | medium | high | high | high | yes | yes |
| exim | medium | low | high | medium | yes | no |
| Courier | low | medium | high | medium | optional | yes |
Sendmailish means the MTA behaves like Sendmail in some ways that would make a switch from Sendmail to the alternative MTA more user-transparent, such as the use of .forward files, /etc/aliases, and delivery to /var/spool/mail.
Jonathan de Boyne Pollard has reviews of many Unix MTAs at http://homepages.tesco.net/~J.deBoynePollard/Reviews/UnixMTSes/. Another detailed comparison is available at http://www.geocities.com/mailsoftware42/.
1.10. Documentation
1.10.1. man pages
The qmail distribution comes with a complete set of man pages. After installation, they're in /var/qmail/man. You'll probably need to add that directory to your MANPATH environment variable.
| Shell | Command |
| Bourne (/bin/sh) | MANPATH=$MANPATH:/var/qmail/man; export MANPATH |
| bash, Korn | export MANPATH=$MANPATH:/var/qmail/man |
| C Shell | setenv MANPATH $MANPATH:/var/qmail/man |
At this point, commands in the format "man name-of-qmail-man-page" should display the appropriate man page.
The man pages are also available on-line in HTML format from:
Note: The qmail man pages are loaded with information, but they require careful reading because they're written in a very dense, technical style. You might want to print off a set and read them through once to familiarize yourself with what's there and where it is. Very little information is repeated on multiple pages, so if you don't know where something is covered, it can be hard to find it.
1.10.2. Docs
The qmail distribution includes a series of documents that are installed under /var/qmail/doc. They include:
- FAQ: Frequently Asked Questions, with answers
- INSTALL*: Installation documentation
- PIC.*: Descriptions of how qmail performs key tasks. See the Architecture appendix for more information.
- Various other installation-related documentation
These docs are also available on-line from:
1.10.3. FAQs
There are two official FAQ (Frequently Asked Questions, with answers) documents:
- /var/qmail/doc/FAQ, the plain text version, and
- The web FAQ at http://cr.yp.to/qmail/faq.html.
The web FAQ is more complete.
1.10.4. Books
<IP_ADDRESS>. The qmail Handbook
Dave Sill, the author of Life with qmail, has written a qmail book for Apress (http://www.apress.com/). This book, The qmail Handbook, covers everything in this guide, but goes into much more detail and also covers a lot of new ground.
For more information, see http://www.apress.com/catalog/book/1893115402/. To order this book from my bookstore, in association with Amazon.com, see http://www.amazon.com/exec/obidos/ASIN/1893115402/davesill.
<IP_ADDRESS>. Qmail Quickstarter: Install, Set Up and Run your own Email Server
Kyle Wheeler has written a qmail book for Packt (http://www.packtpub.com/). As the title suggests, this book is designed to help people new to qmail to set up a mail server.
To order this book from my bookstore, in association with Amazon.com, see http://www.amazon.com/exec/obidos/ASIN/1847191150/davesill.
<IP_ADDRESS>. qmail
John Levine has written a qmail book for O'Reilly & Associates (http://www.oreilly.com/). See http://qmail.gurus.com/ for more info including the Table of Contents and a sample chapter.
To order this book from my bookstore, in association with Amazon.com, see http://www.amazon.com/exec/obidos/ASIN/1565926285/davesill.
<IP_ADDRESS>. Running qmail
Richard Blum has written Running qmail, which is published by Sams. This book has received mixed reviews on the qmail mailing list.
For more information or to order this book, see http://www.amazon.com/exec/obidos/ASIN/0672319454/davesill.
<IP_ADDRESS>. qmail: Yuksek Performansli E-Posta Sunucu
Ismail Yenigul, et al, have written a Turkish-language qmail book. See http://www.acikakademi.com/catalog/qmail/.
1.10.5. List archives
The qmail e-mail mailing list, maintained by Dan Bernstein, is a valuable source of information. Web archives of the lists messages are kept at:
- http://www.ornl.gov/lists/mailing-lists/qmail/.
- http://tech.groups.yahoo.com/group/djb-qmail/?refstop=1 and
- http://securepoint.com/lists/html/Qmail/.
Most questions about qmail can be answered by searching the list archives first.
1.10.6. Other Web Sites
- http://cr.yp.to/qmail.html: the official qmail home page.
- http://www.qmail.org: the unofficial qmail home page. Contains lots of information about add-ons and patches, and links to many good qmail web pages on other sites.
- http://www.flounder.net/qmail/qmail-howto.html: Adam McKenna's HOWTO.
1.11. Support
1.11.1. Mailing lists
The following lists reside on list.cr.yp.to. In order to prevent harvesting of e-mail addresses by spammers, I'm avoiding the use of complete, valid addresses and "mailto" URL's.
The lists are managed by ezmlm, which uses different addresses to perform different functions:
-<EMAIL_ADDRESS>the submission address. Messages sent here go out to all members of the list. Do not send subscribe/unsubscribe requests here: they won't work, and they'll annoy the subscribers.
-<EMAIL_ADDRESS>the "help" address. Returns a list of command addresses and general usage information.
- listname-subscribe: send a blank message here to subscribe.
- listname-unsubscribe: send a blank message here to unsubscribe.
To specify a subscription/unsubscription address, say<EMAIL_ADDRESS>send the message to:
-<EMAIL_ADDRESS><IP_ADDRESS>. qmail
The main qmail mailing list. For discussion and questions/answers on most things related to qmail, except those with their own lists. Read Charles Cazabon's "12 Steps to qmail List Bliss" at http://pyropus.ca/personal/writings/12-steps-to-qmail-list-bliss.html before posting. Also read the FAQs and search the list archives before posting a question. When you ask questions, please try to include sufficient details to make it possible for people to respond:
- What did you do? What's your configuration? Include qmail-showctl output if you're not sure what's important. What action did you take? If this is a new installation, tell how you installed qmail.
- What did you expect to happen? What was the outcome you were trying to achieve? Don't assume the reader can guess.
- What did happen? Describe the actual result. Include log file clippings and copies of messages, with headers.
Note: The qmail list uses a utility called qsecretary to verify that messages posted to the list are not spam. Each message posted to the list will result in an e-mail confirmation request from qsecretary. Read the message and follow the directions to confirm your message--usually just replying to the qsecretary message will do the trick. Regular list posters often automate this process using autoresponders like Charles Cazabon's pymsgauth, available from http://pyropus.ca/software/pymsgauth/. pymsgauth verifies that message sent to the qmail list really came from you, so it won't automatically confirm forged messages sent to the list in your name.
<IP_ADDRESS>. qmailannounce
The qmail announcement mailing list. New releases are announced here. There's no submission address: it's a read-only list.
<IP_ADDRESS>. serialmail
For discussion of the serialmail package.
<IP_ADDRESS>. ezmlm
For discussion of the ezmlm mailing list manager.
1.11.2. Consultants
See http://www.qmail.org/top.html#paidsup for a list of commercial support providers.
1.11.3. FAQTS Knowledgebase
A database of qmail-related questions and answers is available at http://qmail.faqts.com/. If you have a question that the FAQ doesn't answer, try searching this knowledgebase. It's especially good at answering "how to" questions.
2. Installation
This section covers installing qmail. If you're an experienced system administrator, you can install qmail following the directions in INSTALL in the source distribution. The INSTALL directions are the official installation directions. They're more complex than the Life with qmail directions, and they assume that the reader is an experienced system and mail administrator. They're also outdated and don't reflect Bernstein's current recommended practices.
Note: If you choose to install using the following directions, you should read through the entire section to familiarize yourself with the overall process.
2.1. Installation Issues
2.1.1. Binary vs. source code
Before 2007-11-30, qmail's restrictive licensing regarding the distribution of prebuilt packages meant that it was usually installed from a source code distribution. This may change in the future, expecially if daemontools and ucspi-tcp are placed in the public domain. For now, though, source code is still the preferred distribution method for qmail.
If you're not familiar with the distinction between source code and binaries, imagine ordering a pizza delivered to your house. The "binary" version of the pizza arrives ready-to-eat. The "source code" pizza comes as a kit containing flour, yeast, cheese, sauce, toppings, and directions for cooking the pizza yourself. Source code installations are a little more work for you, but if you follow the directions carefully, the result is the same--or even better. The self-baked pizza will be fresher, you can adjust the toppings to your preferences, and you'll know a lot more about your pizza and how it "works".
Safely running an Internet-accesible network service is not easy. An improperly configured service can put the host system at risk of attack or can be used to attack other sites--potentially exposing the administrator to legal liability. The more you know about how your network services work, the more likely they are to be properly configured and secure.
2.1.2. Tarball vs. OS-specific package
Some operating systems provide a mechanism for automating source code installations. Returning to the pizza analogy, they make it possible to package the ingredients and directions in such a way that you can just push a button and have the pizza bake itself.
Sounds great, doesn't it?
In practice, it might not be such a good idea. Assembling these packages is pretty difficult, and they might not do things the way they're supposed to. They're software, and like any software, they can have bugs. But even if they're bug free, the convenience they provide comes at a cost. You lose most of the advantages of the self-baked pizza: the ability to adjust the toppings to your personal preferences, and the knowledge of how the pizza was made and how it works.
If qmail was a pizza, the self-building approach might still be the way to go. But it's not: it's a fairly complicated system that the installer/maintainer needs to understand pretty well in order to be able to keep it working smoothly. The self-installing qmail is easier to install than the user-installed version, but the user-installed version is easier to configure and troubleshoot. You install qmail once on a system, but you will probably have several opportunities to reconfigure it or try to figure out why mail isn't flowing the way you think it should.
For this reason, I suggest installing qmail from scratch using the source code tarball, not a Red Hat RPM or other self-installing bundle.
2.2. Preparation
Before installing qmail on a system, especially if this is your first qmail installation, there are a few things you need to think about.
- If possible, install qmail on a "practice" system. This will give you a chance to make mistakes without losing important mail or interrupting mail service to your users.
- If you don't have a spare, and your system is already handling mail using sendmail, smail, or some other MTA, you can install and test most pieces of qmail without interfering with the existing service.
- When migrating a system from some other MTA to qmail--even if you've got some qmail experience under your belt--it's a good idea to formulate a plan.
2.3. System requirements
qmail will install and run on most UNIX and UNIX-like systems, but there are few requirements:
- About 10 megabytes of free space in the build area during the build. After the build, you can free all but 4 megabytes by removing the object files.
- A complete, functioning C development system including a compiler, system header files, and libraries. The build directions will show you how to tell if you've got the necessary parts.
- A few megabytes for the binaries, documentation, and configuration files.
- A safe filesystem for the queue. qmail's reliability guarantee requires that the queue reside on a filesystem with traditional BSD FFS semantics. Most modern local filesystems meet these requirements with one important exception: the link() system call is often asynchronous--meaning that the results of the link() operation might not have been written to disk when the link() call returns. Bruce Guenter's syncdir library can be used to work around this problem. See syncdir in the Related Packages appendix for more information.
- Sufficient disk space for the queue. Small single-user systems only need a couple megabytes. Large servers may need a couple gigabytes.
- A compatible operating system. Most flavors of UNIX are acceptable. See README in the source tree for a list of known compatible releases.
- Access to a domain name server (DNS) is highly recommended. Without one, qmail can only send to remote systems configured in its smtproutes config file.
- Adequate network connectivity. qmail was designed for well-connected systems, so you probably don't want to try to use it for a mailing list server on a 28.8k dial-up. The serialmail package was designed to make qmail more compatible with poorly-connected systems. See the serialmail section in the Related Packages appendix for more information.
Note: The qmail bin directory must reside on a filesystem that allows the use of executable and setuid() files. Some OS distributions automatically mount /var with the nosuid or noexec options enabled. On such systems, either these options should be disabled or /var/qmail/bin should reside on another filesystem without these options enabled. The Create directories section describes how to use symbolic links to accomplish the latter. If /var is mounted nosuid, you'll probably see the following error message in the qmail-send logs:
delivery : deferral: Sorry,_message_has_wrong_owner._(#4.3.5)
Note: qmail won't install properly under Apple's OS X following these directions or the ones in the INSTALL file. Eben Pratt has documented procedures for installing under OS X, available from http://netdevice.com/qmail/#osx.
2.4. Download the source
OK, so you've got a system meeting the requirements ready for installing qmail. The first step is to download the source code for qmail and any other add-ons. You'll need qmail, of course, and you should probably also get ucspi-tcp and daemontools:
- qmail, http://www.qmail.org/netqmail-1.06.tar.gz
- ucspi-tcp, http://cr.yp.to/ucspi-tcp/ucspi-tcp-0.88.tar.gz
- daemontools, http://cr.yp.to/daemontools/daemontools-0.76.tar.gz
Retrieve these files using your web browser, web client (e.g., wget), or FTP client.
Note: If any of the links fail, it's probably because the package has been updated. In that case, you should go to http://cr.yp.to/software.html and follow the links to download the current version. It's possible that upgraded versions aren't compatible with the following instructions, so be sure to read the release notes in the "Upgrading from previous versions..." sections.
Note: This installation uses the netqmail distribution of qmail, which consists of the official qmail 1.03 tarball to which patches that fix a handful of bugs, deficiencies, and incompatibilities have been applied. See http://www.qmail.org/netqmail/ and the netqmail CHANGES file for more information.
2.5. Build the source
2.5.1. Verify build environment
The first thing you need to do is make sure that you have the necessary tools to compile a program. How you determine this depends on what flavor of UNIX you're using. The easiest way to tell, although it's not guaranteed, is to try it.
Note: If any one of these tests passes, you can stop and go on to the next section.
- At a command line prompt, type cc and press Enter:
$ cc cc: No input files specified $
- If you get a similar response, you have a C compiler in your path. If not, it doesn't necessarily mean you don't have one installed. You might, but maybe it isn't in your path. Of course it could also mean that you don't have one. Try these:
- /usr/bin/cc
- /usr/bin/gcc
- /usr/local/bin/cc
- /usr/local/bin/gcc
- /usr/ccs/bin/cc
- If none of these works, you'll have to try something little more platform specific. At the prompt try one of these, depending on which OS you're using:
- Red Hat Linux: rpm -qa | grep gcc or rpm -qa | grep egcs
- FreeBSD: includes GCC by default
- If you can't find a compiler installed, you'll have to locate one and install it. Contact your OS vendor or other OS support channel.
In this section we'll go through the actual steps of compiling qmail. A way to cut-n-paste will come in handy here, but isn't really necessary.
2.5.2. Unpack the distribution
If you made it this far, you have a working C compiler and copies of the tarballs. Next, copy or move the tarballs to the directory you want to do the work in. /usr/local/src is a good choice for qmail and ucspi-tcp. daemontools should be built under /package.
At this time you probably want to become root, if you're not already.
su umask 022 mkdir -p /usr/local/src mv netqmail-1.06.tar.gz ucspi-tcp-0.88.tar.gz /usr/local/src mkdir -p /package mv daemontools-0.76.tar.gz /package chmod 1755 /package
Now you can unpack the packages.
cd /usr/local/src gunzip netqmail-1.06.tar.gz tar xpf netqmail-1.06.tar gunzip ucspi-tcp-0.88.tar.gz tar xpf ucspi-tcp-0.88.tar rm *.tar # optional, unless space is very tight cd /package gunzip daemontools-0.76.tar.gz tar xpf daemontools-0.76.tar rm *.tar # optional, again
There should now be directories called /usr/local/src/netqmail-1.06, /usr/local/src/ucspi-tcp-0.88, and /package/admin/daemontools-0.76.
2.5.3. Create directories
Since qmail's installation program creates the subdirectories as they're needed, you only need to create the qmail "home" directory:
mkdir /var/qmail
And on to the next section.
Note: If you want some or all of the qmail files to reside elsewhere than /var, this can be accomplished by creating symbolic links under /var/qmail pointing to the other locations.
For example, the qmail configuration files can be stored in /etc/qmail by doing:
mkdir /etc/qmail ln -s /etc/qmail /var/qmail/control
2.5.4. Create users and groups
The easiest way to create the necessary users and groups is to create a little script file to do it for you. In the source directory you'll find a file called INSTALL.ids. It contains the command lines for many platforms, so copying the file to another name and editing that is quick and easy.
cd /usr/local/src/netqmail-1.06 cp INSTALL.ids IDS
Then, using your favorite editor, remove all of the file except the lines you want. For example, here's what IDS would look like for FreeBSD after editing:
pw groupadd nofiles pw useradd qmaild -g nofiles -d /var/qmail -s /nonexistent pw useradd alias -g nofiles -d /var/qmail/alias -s /nonexistent pw useradd qmaill -g nofiles -d /var/qmail -s /nonexistent pw useradd qmailp -g nofiles -d /var/qmail -s /nonexistent pw groupadd qmail pw useradd qmailq -g qmail -d /var/qmail -s /nonexistent pw useradd qmailr -g qmail -d /var/qmail -s /nonexistent pw useradd qmails -g qmail -d /var/qmail -s /nonexistent
Then to run it, either use chmod to make it executable or run it with sh:
First method:
chmod 700 IDS ./IDS
Second method:
/bin/sh IDS
When the script finishes, all of your users and groups will be created and you can go on to the next section.
But what do you do if your system isn't listed in INSTALL.ids? You'll have to create them manually. Start by using your favorite editor and editing /etc/group. You need to add the following two lines to the end of the file:
qmail:*:2107: nofiles:*:2108:
Note: Make sure that 2107 and 2108 aren't already used. If they are used, select two numbers that aren't already in use.
Next, using vipw (most systems have it, if not you'll need to use your editor again but this time on /etc/passwd) add these lines to the end of the file:
alias:*:7790:2108::/var/qmail/alias:/bin/true qmaild:*:7791:2108::/var/qmail:/bin/true qmaill:*:7792:2108::/var/qmail:/bin/true qmailp:*:7793:2108::/var/qmail:/bin/true qmailq:*:7794:2107::/var/qmail:/bin/true qmailr:*:7795:2107::/var/qmail:/bin/true qmails:*:7796:2107::/var/qmail:/bin/true
Note: Make sure 7790-7796 aren't already in use and that 2107 and 2108 are the same group ids you used above. If any of these UID's are already being used, select numbers that aren't already in use.
You don't specifically need to add any of these lines to the end of the file, that's just the easiest way to explain it here.
You're now ready to continue on to the next section.
2.5.5. Do the build
Now you can start building qmail. Change to the /usr/local/src/netqmail-1.05/netqmail-1.05 directory and let's get started:
cd /usr/local/src/netqmail-1.06
In the Verify Build Environment section, you located your C compiler. If it's not called cc or the directory it resides in isn't in your PATH environment variable, you'll need to edit conf-cc and conf-ld. Say your compiler is gcc, and it's in your PATH. Simply edit conf-cc and conf-ld and replace "cc" with "gcc".
Now type the following:
make setup check
After the build is complete, you'll need to do your post installation configuration. A couple of scripts are provided to make this job a lot easier.
 E.g., if your hostname is "mash", you could do ./config-fast mash.local. If you do this, be sure to configure qmail to use a valid Internet domain name in return addresses. (See section 3, Configuration.)
qmail is now installed on your system and is ready to be run! The next section will guide you through the steps of starting and testing qmail.
2.6. Install ucspi-tcp
Earlier, you unpacked the qmail, ucspi-tcp, and daemontools tarballs. Now change to the ucspi-tcp directory:
cd /usr/local/src/ucspi-tcp-0.88
In the Do the build section, if you modified conf-cc and conf-ld, you'll need to make the same changes in this directory.
Then do:
patch < /usr/local/src/netqmail-1.06/other-patches/ucspi-tcp-0.88.errno.patch make make setup check
That's it. ucspi-tcp is installed.
2.7. Install daemontools
Change to the daemontools build directory:
cd /package/admin/daemontools-0.76
Once again, if you modified <conf-cc> and conf-ld during the qmail and ucspi-tcp builds, you'll need to make the same changes in the src directory.
Then do:
cd src patch < /usr/local/src/netqmail-1.06/other-patches/daemontools-0.76.errno.patch cd .. package/install
On BSD systems (no /etc/inittab), you'll need to reboot at this point to start svscan, the master service control daemon.
Use "ps -ef | grep svscan" or "ps waux | grep svscan" to verify that svscan is running.
Note: Under Solaris, you'll have to modify the /etc/inittab entry that starts svscan from:
SV:123456:respawn:/command/svscanboot
to:
SV:123456:respawn:/command/svscanboot </dev/null >/var/log/svscan 2>&1
or:
SV:123456:respawn:/command/svscanboot </dev/null >/dev/msglog 2>&1
Depending upon whether you want error messages resutling from starting svscan to be sent to a log file or the system console. For an explanation of why this is necessary, see:
http://marc.theaimsgroup.com/?l=log&m=100327801309834&w=2
Note: A Slackware user reports that the SV /etc/inittab entry has to be moved before the x1 entry or svscan won't be started at boot-up.
2.8. Start qmail
2.8.1. /var/qmail/rc
The /var/qmail/boot directory contains example qmail boot scripts for different configurations: /var/spool/mail vs. $HOME/Mailbox, using procmail or dot-forward, and various combinations of these. Feel free to examine these, but for our installation, we'll use the following script:
#!/bin/sh # Using stdout for logging # Using control/defaultdelivery from qmail-local to deliver messages by default exec env - PATH="/var/qmail/bin:$PATH" \ qmail-start "`cat /var/qmail/control/defaultdelivery`"
Note: This script uses backquotes (`), not single quotes ('). For best results, copy and paste the scripts in this guide instead of retyping them.
Use your editor to create the above /var/qmail/rc, then execute these commands:
chmod 755 /var/qmail/rc mkdir /var/log/qmail
At this point you need to decide the default delivery mode for messages that aren't delivered by a .qmail file. The following table outlines some common choices.
| Mailbox format | Name | Location | defaultdelivery | Comments |
| mbox | Mailbox | $HOME | ./Mailbox | most common, works with most MUA's |
| maildir | Maildir | $HOME | ./Maildir/ | more reliable, less MUA support |
| mbox | username | /var/spool/mail | See INSTALL.vsm | traditional UNIX mailbox |
See INSTALL.mbox, INSTALL.maildir, and INSTALL.vsm for more information.
To select your default mailbox type, just enter the defaultdelivery value from the table into /var/qmail/control/defaultdelivery. E.g., to select the standard qmail Mailbox delivery, do:
echo ./Mailbox >/var/qmail/control/defaultdelivery
Note: defaultdelivery isn't a standard qmail control file. It's a feature of the above /var/qmail/rc file. The defaultdelivery argument to qmail-start is the contents of a .qmail file that specifies delivery instructions to be followed when no actual .qmail is found. Putting these instructions in a separate control file eliminates the need to quote shell metacharacters in the delivery instructions and avoids messy multi-line command arguments.
2.8.2. System start-up files
<IP_ADDRESS>. The qmailctl script
If you were to manually execute the /var/qmail/rc script, qmail would be partially started. But we want qmail started up automatically every time the system is booted and we want it shut down cleanly when the system is halted.
This is accomplished by creating a startup/shutdown script like the following in /var/qmail/bin/qmailctl:
#!/bin/sh # description: the qmail MTA PATH=/var/qmail/bin:/bin:/usr/bin:/usr/local/bin:/usr/local/sbin export PATH QMAILDUID=`id -u qmaild` NOFILESGID=`id -g qmaild` case "$1" in start) echo "Starting qmail" if svok /service/qmail-send ; then svc -u /service/qmail-send /service/qmail-send/log else echo "qmail-send supervise not running" fi if svok /service/qmail-smtpd ; then svc -u /service/qmail-smtpd /service/qmail-smtpd/log else echo "qmail-smtpd supervise not running" fi if [ -d /var/lock/subsys ]; then touch /var/lock/subsys/qmail fi ;; stop) echo "Stopping qmail..." echo " qmail-smtpd" svc -d /service/qmail-smtpd /service/qmail-smtpd/log echo " qmail-send" svc -d /service/qmail-send /service/qmail-send/log if [ -f /var/lock/subsys/qmail ]; then rm /var/lock/subsys/qmail fi ;; stat) svstat /service/qmail-send svstat /service/qmail-send/log svstat /service/qmail-smtpd svstat /service/qmail-smtpd/log qmail-qstat ;; doqueue|alrm|flush) echo "Flushing timeout table and sending ALRM signal to qmail-send." /var/qmail/bin/qmail-tcpok svc -a /service/qmail-send ;; queue) qmail-qstat qmail-qread ;; reload|hup) echo "Sending HUP signal to qmail-send." svc -h /service/qmail-send ;; pause) echo "Pausing qmail-send" svc -p /service/qmail-send echo "Pausing qmail-smtpd" svc -p /service/qmail-smtpd ;; cont) echo "Continuing qmail-send" svc -c /service/qmail-send echo "Continuing qmail-smtpd" svc -c /service/qmail-smtpd ;; restart) echo "Restarting qmail:" echo "* Stopping qmail-smtpd." svc -d /service/qmail-smtpd /service/qmail-smtpd/log echo "* Sending qmail-send SIGTERM and restarting." svc -t /service/qmail-send /service/qmail-send/log echo "* Restarting qmail-smtpd." svc -u /service/qmail-smtpd /service/qmail-smtpd/log ;; cdb) tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp chmod 644 /etc/tcp.smtp.cdb echo "Reloaded /etc/tcp.smtp." ;; help) cat <<HELP stop -- stops mail service (smtp connections refused, nothing goes out) start -- starts mail service (smtp connection accepted, mail can go out) pause -- temporarily stops mail service (connections accepted, nothing leaves) cont -- continues paused mail service stat -- displays status of mail service cdb -- rebuild the tcpserver cdb file for smtp restart -- stops and restarts smtp, sends qmail-send a TERM & restarts it doqueue -- schedules queued messages for immediate delivery reload -- sends qmail-send HUP, rereading locals and virtualdomains queue -- shows status of queue alrm -- same as doqueue flush -- same as doqueue hup -- same as reload HELP ;; *) echo "Usage: $0 {start|stop|restart|doqueue|flush|reload|stat|pause|cont|cdb|queue|help}" exit 1 ;; esac exit 0
This script is available via http://lifewithqmail.org/qmailctl-script-dt70.
Create the script using your editor or by downloading it with your web browser (recommended).
Make the qmailctl script executable and link it to a directory in your path:
chmod 755 /var/qmail/bin/qmailctl ln -s /var/qmail/bin/qmailctl /usr/bin
<IP_ADDRESS>. The supervise scripts
Now create the supervise directories for the qmail services:
mkdir -p /var/qmail/supervise/qmail-send/log mkdir -p /var/qmail/supervise/qmail-smtpd/log
Create the /var/qmail/supervise/qmail-send/run file:
#!/bin/sh exec /var/qmail/rc
Create the /var/qmail/supervise/qmail-send/log/run file:
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t /var/log/qmail
Create the /var/qmail/supervise/qmail-smtpd/run file:
#!/bin/sh QMAILDUID=`id -u qmaild` NOFILESGID=`id -g qmaild` MAXSMTPD=`cat /var/qmail/control/concurrencyincoming` LOCAL=`head -1 /var/qmail/control/me` if [ -z "$QMAILDUID" -o -z "$NOFILESGID" -o -z "$MAXSMTPD" -o -z "$LOCAL" ]; then echo QMAILDUID, NOFILESGID, MAXSMTPD, or LOCAL is unset in echo /var/qmail/supervise/qmail-smtpd/run exit 1 fi if [ ! -f /var/qmail/control/rcpthosts ]; then echo "No /var/qmail/control/rcpthosts!" echo "Refusing to start SMTP listener because it'll create an open relay" exit 1 fi exec /usr/local/bin/softlimit -m 2000000 \ /usr/local/bin/tcpserver -v -R -l "$LOCAL" -x /etc/tcp.smtp.cdb -c "$MAXSMTPD" \ -u "$QMAILDUID" -g "$NOFILESGID" 0 smtp /var/qmail/bin/qmail-smtpd 2>&1
Note: concurrencyincoming isn't a standard qmail control file. It's a feature of the above script. Also, that's -1 (dash one) on the LOCAL line and -l (dash ell) on the tcpserver line.
Note: Under Solaris, the normal id program won't work right in this script. Instead of id, use /usr/xpg4/bin/id, e.g.:
QMAILDUID=`/usr/xpg4/bin/id -u qmaild` NOFILESGID=`/usr/xpg4/bin/id -g qmaild`
Note: The memory limit specified in the softlimit command may need to be raised depending upon your operating system and hardware platform. If attempts to connect to port 25 fail or remote systems are unable to send you mail, or you see a message like:
/usr/local/bin/tcpserver: error while loading shared libraries: libc.so.6: failed to map segment from shared object: Cannot allocate memory
try raising it to 3000000 or 4000000.
Create the concurrencyincoming control file:
echo 20 > /var/qmail/control/concurrencyincoming chmod 644 /var/qmail/control/concurrencyincoming
Create the /var/qmail/supervise/qmail-smtpd/log/run file:
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t /var/log/qmail/smtpd
Make the run files executable:
chmod 755 /var/qmail/supervise/qmail-send/run chmod 755 /var/qmail/supervise/qmail-send/log/run chmod 755 /var/qmail/supervise/qmail-smtpd/run chmod 755 /var/qmail/supervise/qmail-smtpd/log/run
Then set up the log directories:
mkdir -p /var/log/qmail/smtpd chown qmaill /var/log/qmail /var/log/qmail/smtpd
Finally, link the supervise directories into /service:
ln -s /var/qmail/supervise/qmail-send /var/qmail/supervise/qmail-smtpd /service
The /service directory is created when daemontools is installed.
Note: The qmail system will start automatically shortly after these links are created. If you don't want it running yet, do:
qmailctl stop
<IP_ADDRESS>. SMTP Access Control
Allow the local host to inject mail via SMTP:
echo '127.:allow,RELAYCLIENT=""' >>/etc/tcp.smtp qmailctl cdb
2.8.3. Stop and disable the installed MTA
Although it's possible to run both qmail and your existing MTA, which is probably Sendmail, simultaneously, I don't recommend it unless you know what you're doing. And, frankly, if you're reading this, you probably don't know what you're doing. :-)
If your existing MTA is Sendmail, you should be able to stop it by running the init.d script with the "stop" argument. E.g., one of these should work:
/etc/init.d/sendmail stop /sbin/init.d/sendmail stop /etc/rc.d/init.d/sendmail stop
If you can't find an init.d/sendmail script, you can locate sendmail's PID using "ps -ef|grep sendmail" or "ps waux|grep sendmail" and stop it using:
kill PID-of-sendmail
If your MTA isn't Sendmail, check its documentation for the correct shutdown procedure.
You should also consider removing the old MTA completely from the system. At least disable the init.d script so it doesn't try to start up again when the system is rebooted.
For Red Hat Linux, removing Sendmail can be accomplished by:
rpm -e --nodeps sendmail
Note: If you're using an RPM-based Linux distribution like Red Hat, removing the MTA package might cause problems down the road. Utilities that update the system might try to reinstall Sendmail, or MUA packages might not install because they can't tell an MTA is installed. Mate Wierdl provides a stub package called "fake_mta" that can be installed to prevent these problems. Simply install the RPM available from ftp://ftp.csi.hu/mw/fake_mta-1-10memphis.noarch.rpm .
Verify that nothing is listening to the SMTP port (25). Culprits could be the old MTA, inetd, or xinetd. The following command should produce no output (unless the qmail-smtpd service is running):
netstat -a | grep smtp
If something is running, make sure it's not qmail by doing:
qmailctl stop
The repeat the netstat check:
netstat -a | grep smtp
If you still get output from that command you'll have to locate the culprit and fix it before qmail's SMTP service will run.
Lastly, replace any existing /usr/lib/sendmail with the qmail version:
mv /usr/lib/sendmail /usr/lib/sendmail.old # ignore errors mv /usr/sbin/sendmail /usr/sbin/sendmail.old # ignore errors chmod 0 /usr/lib/sendmail.old /usr/sbin/sendmail.old # ignore errors ln -s /var/qmail/bin/sendmail /usr/lib ln -s /var/qmail/bin/sendmail /usr/sbin
Note: It's important to create the sendmail links, regardless of the previous MTA, if any. The sendmail command is invoked by many applications for sending mail.
The last step is to create a couple of system aliases.
2.8.4. Create System Aliases
There are three system aliases that should be created on all qmail installations:
| Alias | Purpose |
| postmaster | RFC 2821 required, points to the mail adminstrator (you) |
| mailer-daemon | de facto standard recipient for some bounces |
| root | redirects mail from privileged account to the system administrator |
| abuse | de facto standard recipient for abuse complaints |
To create these aliases, decide where you want each of them to go (a local user or a remote address) and create and populate the appropriate .qmail files. For example, say local user dave is both the system and mail administrator:
echo dave > /var/qmail/alias/.qmail-root echo dave > /var/qmail/alias/.qmail-postmaster ln -s .qmail-postmaster /var/qmail/alias/.qmail-mailer-daemon ln -s .qmail-postmaster /var/qmail/alias/.qmail-abuse chmod 644 /var/qmail/alias/.qmail-root /var/qmail/alias/.qmail-postmaster
See INSTALL.alias for more details.
2.8.5. Start qmail
If you stopped qmail above after creating the links in /service, you should restart it now:
qmailctl start
2.9. Test the Installation
qmail should now be running. First run qmailctl stat to verify that the services are up and running:
# qmailctl stat /service/qmail-send: up (pid 30303) 187 seconds /service/qmail-send/log: up (pid 30304) 187 seconds /service/qmail-smtpd: up (pid 30305) 187 seconds /service/qmail-smtpd/log: up (pid 30308) 187 seconds messages in queue: 0 messages in queue but not yet preprocessed: 0
All four services should be "up" for more than a second. If they're not, you've probably got a typo in the associated run script or you skipped one or more steps in creating the necessary files, directories, or links. Go back through the installation step-by-step and double check your work. You can also download and run the inst_check script, available from http://lifewithqmail.org/inst_check. For example:
# sh inst_check ! /var/log/qmail has wrong owner, should be qmaill ...try: chown qmaill /var/log/qmail #
If inst_check finds problems, fix them and re-run it. When everything looks right, inst_check will report:
Congratulations, your LWQ installation looks good!
The readproctitle program keeps a log of error messages generated by services managed by svscan. To see these messages, use ps or some other process listing command. For example, you might see something like:
# ps -efl | grep "service errors" | grep -v grep 000 S root 1006 1001 0 76 0 - 334 pipe_w Mar31 ? 00:00:00 readproctitle service errors: ...unable to start qmail-smtpd/run: exec format error #
In this case, the problem is that there is an error in the first line of the /service/qmail-smtpd/run script--most likely caused by the file being is DOS format (CR-LF line endings instead of Unix's LF-only).
It sometimes helps to run a service manually in order to find configuration problems. For example, if your qmail-smtpd/log service isn't running, do:
cd /service/qmail-smtpd/log svc -d . ./run if no errors, enter a line of text and press ENTER if still no errors, enter CTRL-D (end of file)
At this point, you should be able to identify the problem and fix it. Once that's done, return to the service's directory, if necessary, and do:
svc -u .
Once the services are all up with >1 second uptime, follow the instructions in TEST.deliver and TEST.receive to verify that they're working correctly. Note that using these instructions, logging will be accomplished by multilog to /var/log/qmail, not splogger to something like /var/log/maillog.
Note: If you chose maildir mailbox format as the default delivery method, you will need to create a Maildir directory in your home directory and alias's home directory before trying these instructions. See the maildir section to see how to properly create this directory.
3. Configuration
You've got qmail installed, from the recommended source tarball method, one of the self-compiling packages, or a var-qmail package. This section contains information you will need to configure qmail to make it work the way you want it to.
3.1. Configuration Files
All of qmail's system configuration files, with the exception of the .qmail files in ~alias, reside in /var/qmail/control. The qmail-control man page contains a table like the following:
| Control | Default | Used by | Purpose |
| badmailfrom | none | qmail-smtpd | blacklisted From addresses |
| bouncefrom | MAILER-DAEMON | qmail-send | username of bounce sender |
| bouncehost | me | qmail-send | hostname of bounce sender |
| concurrencyincoming | none | /service/qmail-smtpd/run | max simultaneous incoming SMTP connections |
| concurrencylocal | 10 | qmail-send | max simultaneous local deliveries |
| concurrencyremote | 20 | qmail-send | max simultaneous remote deliveries |
| defaultdelivery | none | /var/qmail/rc | default .qmail file |
| defaultdomain | me | qmail-inject | default domain name |
| defaulthost | me | qmail-inject | default host name |
| databytes | 0 | qmail-smtpd | max number of bytes in message (0=no limit) |
| doublebouncehost | me | qmail-send | host name of double bounce sender |
| doublebounceto | postmaster | qmail-send | user to receive double bounces |
| envnoathost | me | qmail-send | default domain for addresses without "@" |
| helohost | me | qmail-remote | host name used in SMTP HELO command |
| idhost | me | qmail-inject | host name for Message-ID's |
| localiphost | me | qmail-smtpd | name substituted for local IP address |
| locals | me | qmail-send | domains that we deliver locally |
| me | FQDN of system | various | default for many control files |
| morercpthosts | none | qmail-smtpd | secondary rcpthosts database |
| percenthack | none | qmail-send | domains that can use "%"-style relaying |
| plusdomain | me | qmail-inject | domain substituted for trailing "+" |
| qmqpservers | none | qmail-qmqpc | IP addresses of QMQP servers |
| queuelifetime | 604800 | qmail-send | seconds a message can remain in queue |
| rcpthosts | none | qmail-smtpd | domains that we accept mail for |
| smtpgreeting | me | qmail-smtpd | SMTP greeting message |
| smtproutes | none | qmail-remote | artificial SMTP routes |
| timeoutconnect | 60 | qmail-remote | how long, in seconds, to wait for SMTP connection |
| timeoutremote | 1200 | qmail-remote | how long, in seconds, to wait for remote server |
| timeoutsmtpd | 1200 | qmail-smtpd | how long, in seconds, to wait for SMTP client |
| virtualdomains | none | qmail-send | virtual domains and users |
For more information about a particular control file, see the man page for the module listed under "Used by".
3.2. Relaying
3.2.1. Introduction
What is relaying? It's when an MTA accepts a message via SMTP that doesn't appear to be either for a local address or from a local sender.
In the pre-spam days, it was common for MTA's to be configured as open relays: promiscuous servers that would accept mail from anyone, for anyone.
Most MTA's now are configured to either completely disable relaying, or to only a allow certain trusted users or systems to use them as a relay.
Chris Johnson has written a very nice document on the topic for qmail users. I encourage you to visit http://www.palomine.net/qmail/relaying.html.
3.2.2. Disabling relaying
If you follow the official directions for installing qmail, relaying will be turned off by default. This is accomplished by populating the file /var/qmail/control/rcpthosts with the fully-qualified domain names listed in locals and virtualdomains (the local hosts). The name of the control file, rcpthosts, comes from the SMTP RCPT (recipient) command. In an SMTP session, RCPT is used to specify the addresses of the recipients of a message. rcpthosts, then, lists the valid hostnames that can appear in a RCPT address.
3.2.3. Allowing selective relaying
Most single-user and small workgroup servers can disable relaying completely, but if you have to support a distributed user community, you'll need a way to allow your users, and only your users, to use your system as a relay. This is accomplished by using tcpserver to set the RELAYCLIENT environment variable, which tells qmail-smtpd to override the rcpthosts file.
If you follow the installation instructions in this document, selective relaying will be enabled by default. To give a client relay access, add an entry to /etc/tcp.smtp like:
IP address of client:allow,RELAYCLIENT=""
Then rebuild the SMTP access database by doing:
qmailctl cdb
or:
tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp chmod 644 /etc/tcp.smtp*
If you followed the official installation instructions, Chris Johnson has written another very nice document on how to configure qmail to allow selected hosts to relay. See http://www.palomine.net/qmail/selectiverelay.html.
3.2.4. Relaying to a smart host
For anyone setting up a mail server on a typical home broadband service, there is a good chance that your IP address will get blacklisted by organizations like SORBS (http://www.dnsbl.sorbs.net/lookup.shtml) in an effort to block spam. Most ISPs provide an SMTP server that will relay all mail from their customers, and such servers are usually not blacklisted. For example, the Road Runner service in Cincinnati, Ohio, has smtp-server.cinci.rr.com available to their customers. You can tell qmail to route all outgoing SMTP traffic through that server by doing:
echo ":smtp-server.cinci.rr.com" > /var/qmail/control/smtproutes
The smtproutes file can perform more routing functions than this; see the qmail-remote man page for more details.
3.3. Multiple host names
If your system is known by more than one name, e.g., all addresses of the form<EMAIL_ADDRESS>can also be written as<EMAIL_ADDRESS>or<EMAIL_ADDRESS>then you need to tell qmail this so it'll know which addresses it should deliver locally and which messages it should accept from remote systems.
To do this, just add all of the names to two control files:
- rcpthosts, which tells qmail-smtpd to accept mail addressed to these hosts, and
- locals, which tells qmail-send that addresses on these hosts are to be delivered locally.
Send qmail-send a HUP (hangup) signal to tell it to reread locals. If you have qmailctl, you can do:
qmailctl reload
3.4. Virtual domains
Virtual domains are similar to the multiple host names discussed in the previous section, but there are some important differences. First, if example.net hosts the virtual domain virtual.example.com, it's generally not true that messages sent to<EMAIL_ADDRESS>should end up in the same mailbox as messages sent to<EMAIL_ADDRESS>The namespace for each virtual domain is distinct.
With qmail, virtual domains are configured in the virtualdomains file, which consists of one or more entries of the form:
user@domain:prepend
qmail converts user@domain to prepend-user@domain and treats the result as if domain was local. The user@ part is optional. If it's omitted, the entry matches all @domain addresses.
Returning to the example scenario above, if the example.net mail administrator wanted to create a virtual domain, virtual.example.com, under the administrative control of user john, the following entry in virtualdomains would accomplish that:
virtual.example.com:john
An incoming message to<EMAIL_ADDRESS>would be rewritten as<EMAIL_ADDRESS>and delivered locally. See the .qmail section, and the extension addresses subsection for more information about how john can manage his virtual domain.
As with multiple host names, all virtual domains must be listed in rcpthosts so qmail-smtpd will know to accept messages addressed to them. However, unlike multiple host names, virtual domains must not be added to locals.
After modifying virtualdomains, send qmail-send a HUP (hangup) signal to tell it to reread the file. If you have qmailctl, you can do:
qmailctl reload
Don't forget to add virtual domains to rcpthosts, too.
Note: Domain name server (DNS) mail exchanger (MX) records must be set up to direct messages for virtual domains to the appropriate mail server. This is a job for the name server administrator and is beyond the scope of this guide.
3.5. Aliases
qmail's standard aliasing mechanism is a natural outgrowth of qmail's local delivery mechanism. qmail-local attempts to deliver a message addressed to localpart@host to a local user named localpart. If no matching user is found, the message is delivered to the alias user, a pseudo-user on all qmail systems whose home directory is usually /var/qmail/alias.
For example, say you want to create an<EMAIL_ADDRESS>alias that forwards messages to user tom. On example.com, do, as user root:
echo \&tom > /var/qmail/alias/.qmail-info
The .qmail section and extension addresses subsection describe how to create .qmail files that specify which aliases exist, and what to do with messages sent to them.
The Gotchas appendix covers a couple of tricky cases regarding the usage of alias--aliases containing uppercase characters and dots ('.')--and man dot-qmail contains complete documentation of the usage of .qmail files.
Note that because of the way aliases are implemented in qmail, an alias can never override a valid user's deliveries. E.g., if rachel is a normal user, ~alias/.qmail-rachel will not be used.
The fastforward package provides an alternative aliasing mechanism that puts multiple aliases in a single file compatible with Sendmail's alias database.
The next section, qmail-users, describes another mechanism that can be used to implement aliases.
3.6. qmail-users
qmail-users is a system for assigning addresses to users. A series of configuration files resides under /var/qmail/users. The assign file is a table of assignments. There are two kinds of assignments: simple and wildcard.
Note: assign contains a series of assignments, one per line, followed by a line containing a single dot (.). If you create assign manually, don't forget the dot line.
3.6.1. Simple assignment
A simple assignment looks like:
=address:user:uid:gid:directory:dash:extension:
What this means is that messages received for address will be delivered as user user, with the specified uid and gid, and the file directory/.qmaildashextension will specify how the messages are to be delivered.
3.6.2. Wildcard assignment
A wildcard assignment looks like:
+prefix:user:uid:gid:directory:dash:prepend:
What this means is that messages received for addresses of the form prefixrest will be delivered as user user, with the specified uid and gid, and the file directory/.qmaildashprependrest will specify how the messages are to be delivered.
3.6.3. qmail-user programs
qmail-user has two helper programs: qmail-newu and qmail-pw2u.
qmail-newu processes the assign file and generates a constant database (CDB) file called cdb in /var/qmail/users. CDB is a binary format that can be accessed quickly by qmail-lspawn, even when there are thousands of assignments.
qmail-pw2u converts the system user database, /etc/passwd, into a series of assignments suitable for assign. qmail-pw2u uses a set of files to modify the translation rules.
- include: users to include
- exclude: users to exclude
- mailnames: alternative "mailnames" for users
- subusers: extra addresses handled by a user, with an optional .qmail extension
- append: miscellaneous assignments
Note: If you use qmail-pw2u, don't forget to re-run qmail-pw2u and qmail-newu whenever you add users, remove users, or change UID's or GID's. A typical sequence would be:
qmail-pw2u </etc/passwd >/var/qmail/users/assign qmail-newu
3.7. Spam Control
Chris Hardie has written an excellent qmail Anti-Spam HOWTO. It's available from http://www.summersault.com/chris/techno/qmail/qmail-antispam.html.
3.8. Virus Scanning
Jason Haar has written Qmail-Scanner, a content scanning harness for qmail. See http://qmail-scanner.sourceforge.net/ for more information.
Qmail-Scanner includes a simple "policy-blocking" component (e.g. block *.scr, or block "Subject: Yellow!") as well as directly supporting many different antivirus "plugins" including the ClamAV Antivirus scanner available from http://www.ClamAV.net.
4. Usage
This section covers the usage of qmail by normal users. If you read or send mail on a qmail system, this is where you'll find information about how to do that with qmail.
4.1. .qmail files
Delivery of a user's mail is usually controlled by one or more ".qmail" (pronounced dot kyoo mail) files--files in the user's home directory with names beginning with .qmail. The dot-qmail man page describes .qmail file usage.
.qmail files contain a list of delivery instructions, one instruction per line. The first character of the line determines what kind of delivery is involved:
| Character | Delivery Type | Value |
| # | none (comment) | ignored |
| | | program | command to be run by shell |
| / or . | mbox (if last char isn't a /) | pathname of mbox (including the / or .) |
| / or . | maildir (if last char is a /) | pathname of maildir (including the / or .) |
| & | forward | address to forward message |
| letter or number | forward | address to forward message (including the first char) |
4.1.1. program delivery
When a program delivery instruction is encountered, qmail starts a shell (/bin/sh) to execute the command and feeds the command a copy of the incoming message on standard input. The qmail-command man page documents the details of this process.
Program delivery is very powerful, and can be used to implement a wide range of functionality such as message filtering, automatically responding to messages, and delivery via third-party delivery agents such as procmail.
E.g.:
|preline /usr/ucb/vacation djb
This causes qmail to start preline, pass it /usr/ucb/vacation and djb as arguments, and provide a copy of the message on standard input.
4.1.2. mbox delivery
Mbox is the standard UNIX mailbox format in which multiple messages are stored in a single file and messages are headed with a "From " line. This line looks like a header field, but it isn't one: it's just something the delivery agent adds so mail readers can tell where each message begins.
E.g.:
./Mailbox
This causes messages to be appended to $HOME/Mailbox, with a "From " line prepended. A simple mbox mailbox with a single message looks like:
From<EMAIL_ADDRESS>Thu May 13 18:34:50 1999 Received: (qmail 1287205 invoked from network); 13 May 1999 18:34:49 -0000 From<EMAIL_ADDRESS>To<EMAIL_ADDRESS>Subject: hey What's up?
The first line was added at delivery by qmail.
4.1.3. maildir delivery
Maildir is a mailbox format created by Dan Bernstein to address the shortcomings of the mbox format. A maildir mailbox is a directory containing three subdirectories, new, cur, and tmp. Each message in a maildir mailbox is in a separate file in one of the subdirectories, depending upon its status: new is for unread messages, cur is for messages that have been seen, and tmp is for messages in the process of being delivered. The maildir man page describes the format of a maildir in detail.
One of the benefits of the maildir format is that, even though it doesn't use locking to prevent simultaneous updates from different delivery agents, it's reliable. This means maildir mailboxes can safely reside on NFS-mounted filesystems.
E.g.:
./Maildir/
This causes messages to be saved in $HOME/Maildir, a maildir-format mailbox.
Note: qmail-local can deliver mail to maildir mailboxes, but it can't create them. Maildir mailboxes should be created with the maildirmake program that comes with qmail. E.g., "maildirmake ~/Maildir". Be sure to run maildirmake as the owner of the maildir, not as root. Your useradd or adduser command might support a "skeleton" directory, e.g. /etc/skel, where you can create a maildir that will be copied for all new users.
4.1.4. forward delivery
Forward deliveries causes the message to be resent to the specified address. Addresses specified in .qmail files can't contain comment fields or extra spaces.
These are wrong:
<EMAIL_ADDRESS>&<EMAIL_ADDRESS>&Joe User<EMAIL_ADDRESS>These are correct:
<EMAIL_ADDRESS><EMAIL_ADDRESS>&user
The first two cause<EMAIL_ADDRESS>to receive a copy of the message. The last sends a copy to the local user user.
4.1.5. extension addresses
qmail supports user-controlled extension addresses. In addition to the base address<EMAIL_ADDRESS>users can receive mail at<EMAIL_ADDRESS>For the remainder of this section, I'll leave off the<EMAIL_ADDRESS>part since we're considering actions that take place on the local system.
The delivery instructions for username are in ~username/.qmail and the delivery instructions for username-extension are in ~username/.qmail-extension.
For example<EMAIL_ADDRESS>is controlled by ~dave/.qmail-lwq on host sparge.
Extensions can have multiple fields, e.g., dave-list-qmail, controlled by ~dave/.qmail-list-qmail. In this example, dave-list-qmail is subscribed to the qmail mailing list, and ~dave/.qmail-list-qmail files the list messages in a separate mailbox.
.qmail files can be wildcarded using -default. So dave-list-qmail could also be handled by ~dave/.qmail-list-default. This would allow one catch-all .qmail file to handle all dave-list-whatever addresses. Note that dave-list wouldn't be handled by ~dave/.qmail-list-default because it doesn't match the "-" after "list".
qmail uses the closest match it finds. E.g., when a message comes in addressed to dave-list-qmail, it'll use the first one of the following that it finds:
.qmail-list-qmail .qmail-list-default .qmail-default
If no matching .qmail file is found, the delivery fails and the message bounces back to the sender.
4.2. Sending messages
Mail users usually don't use the MTA directly to send messages. Typically, messages are composed and sent using a Mail User Agent (MUA) such as pine or mutt, which then calls the MTA to deliver the message. The process of handing a message to the MTA is called injection.
There are two ways to inject messages into most MTA's: via the Simple Mail Transfer Protocol, SMTP, or using a program provided by the MTA for that purpose.
4.2.1. SMTP
MUA's can open a TCP connection to port 25, the standard SMTP port, on the local host or a designated mail server. The MUA and the MTA then engage in a dialogue that results in either:
- the message being transfered to the MTA, or
- a error status being returned to the MUA
SMTP has no mechanism for authentication, so no username or password is required to send a message. However, many MTA's refuse to accept messages that don't appear to be either from or for a local user. If a properly formatted message is rejected, relaying restrictions are the most likely cause. See the Relaying section for more information about relay configuration.
4.2.2. /var/qmail/bin/sendmail
For many years, Sendmail was the UNIX MTA. It was so ubiquitous, that many programmers just assumed that it was the MTA. As a result, Sendmail's local injection mechanism became the standard Application Programmer's Interface (API) for local mail injection. qmail and other non-Sendmail MTA's provide a sendmail program that works the same way as the real Sendmail's sendmail for local injection.
The qmail sendmail, which is normally in /var/qmail/bin/sendmail, usually replaces the Sendmail sendmail on qmail systems. Typical locations of the sendmail program include:
- /usr/lib/sendmail
- /usr/sbin/sendmail
On a qmail system, "ls -l path-to-sendmail" should show that sendmail is a symbolic link to /var/qmail/bin/sendmail:
$ ls -l /usr/lib/sendmail lrwxrwxrwx 1 root root 29 Feb 19 11:04 /usr/lib/sendmail -> /var/qmail/bin/sendmail
4.2.3. qmail-inject
In addition to emulating the sendmail API, qmail has its own injection program: qmail-inject. In fact, sendmail is just a wrapper around qmail-inject.
As an API, sendmail is probably better because it's much more widely available. The qmail API provided by qmail-inject will only work on systems with qmail, but the sendmail interface is nearly universal.
For example, to send a blank message to<EMAIL_ADDRESS>echo To<EMAIL_ADDRESS>| /var/qmail/bin/qmail-inject
4.3. Environment Variables
Some qmail programs set or use environment variables. The following table lists these variables and describes their use.
| Name | Man page | Set or used | Purpose |
| DATABYTES | qmail-smtpd | used | Overrides control/databytes |
| DEFAULT | qmail-command | set | Portion of address matching "-default" in a .qmail file name. |
| DTLINE | qmail-command | set | Delivered-To header field |
| EXT | qmail-command | set | The address extension |
| EXT2 | qmail-command | set | Portion of EXT following first dash |
| EXT3 | qmail-command | set | Portion of EXT following second dash |
| EXT4 | qmail-command | set | Portion of EXT following third dash |
| HOME | qmail-command | set | The user's home directory |
| HOST | qmail-command | set | The domain part of the recipient address |
| HOST2 | qmail-command | set | Portion of HOST preceding last dot. |
| HOST3 | qmail-command | set | Portion of HOST preceding second-to-last dot |
| HOST4 | qmail-command | set | Portion of HOST preceding third-to-last dot |
| LOCAL | qmail-command | set | The local part of the recipient address |
| LOGNAME | qmail-inject | used | User name in From header field (4) |
| MAILHOST | qmail-inject | used | Host name in From header field (2) |
| MAILNAME | qmail-inject | used | Personal name in From header field (2) |
| MAILUSER | qmail-inject | used | User name in From header field (2) |
| NAME | qmail-inject | used | Personal name in From header field (3) |
| NEWSENDER | qmail-command | set | Forwarding sender address (see "man dot-qmail") |
| QMAILDEFAULTDOMAIN | qmail-inject | used | Overrides control/defaultdomain |
| QMAILDEFAULTHOST | qmail-inject | used | Overrides control/defaulthost |
| QMAILHOST | qmail-inject | used | Host name in From header field (1) |
| QMAILIDHOST | qmail-inject | used | Overrides control/idhost |
| QMAILINJECT | qmail-inject | used | Specify various options (see next table) |
| QMAILMFTFILE | qmail-inject | used | File containing list of mailing list addresses for Mail-Followup-To generation |
| QMAILNAME | qmail-inject | used | Personal name in From header field (1) |
| QMAILPLUSDOMAIN | qmail-inject | used | Overrides control/plusdomain |
| QMAILSHOST | qmail-inject | used | Host name in envelope sender address |
| QMAILSUSER | qmail-inject | used | User name in envelope sender address |
| QMAILUSER | qmail-inject | used | User name in From header field (1) |
| RECIPIENT | qmail-command | set | Envelope recipient address |
| RELAYCLIENT | qmail-smtpd | used | Ignore control/rcpthosts and append value to recipient address |
| RPLINE | qmail-command | set | Return-Path header field |
| SENDER | qmail-command | set | Envelope sender address |
| UFLINE | qmail-command | set | UUCP-style "From " line |
| USER | qmail-command | set | The current user |
| USER | qmail-inject | used | User name in From header field (3) |
| Letter | Purpose |
| c | Use address-comment style for the From field |
| s | Do not look at any incoming Return-Path field |
| f | Delete any incoming From field |
| i | Delete any incoming Message-ID field |
| r | Use a per-recipient VERP |
| m | Use a per-message VERP |
5. Advanced Topics
5.1. procmail
procmail is a popular Message Delivery Agent (MDA). The function of an MDA is to accept a message from the MTA for a specific user or mailbox, and deliver the message according to the user's desires. procmail can be used to "filter" messages by the content of various header fields or the body of the message. For example, messages from a particular person can be directed to a mailbox for just that person.
There are a couple tricks to running procmail with qmail. First, procmail is usually built to deliver to an mbox mailbox in /var/spool/mail. You can rebuild procmail to default to $HOME or you can instruct users not to rely on procmail to default the location of the mbox. Unless you patch it for $HOME delivery, procmail will still use /var/spool/mail for temporary files.
Another problem is that qmail-command and procmail don't have a common understanding of which exit codes mean what. procmail uses the standard UNIX exit codes: zero means success, nonzero means failure, and the cause of the failure is indicated by /usr/include/sys/errno.h. qmail-command uses certain nonzero codes to indicate permanent errors and the rest are considered temporary. A small shell script wrapper can be used to translate the exit codes for qmail-command. Such a wrapper was posted to the qmail list and is available from the archives at http://www.ornl.gov/lists/mailing-lists/qmail/1998/04/msg00487.html.
Also, older versions of procmail (prior to 3.14) don't deliver directly to maildir-format mailboxes. Your best bet is to upgrade to the current version of procmail. Another approach is safecat, a program that writes a message on standard input to a specified maildir. Users can write procmail recipes (delivery instructions) that use safecat to file the message. You can also skip procmail altogether, and use maildrop.
Finally, procmail expects the messages it receives to be in mbox format. Normal qmail program deliveries include only the actual mail message, not including a "From " line. The preline command can be used to format the message as procmail expects. The wrapper linked above includes preline.
For example, let's say user "dave" wants his mail to be processed by procmail. His system administrator has built procmail to deliver to $HOME by default, and has provided the exit code wrapper linked above, called /usr/local/bin/qmail-procmail. His .qmail file should look like:
|/usr/local/bin/qmail-procmail
5.2. POP and IMAP servers
qmail includes a POP server, qmail-pop3d, but it's not configured and installed as part of the qmail installation process. You can also use one of the other POP or IMAP servers available, although most of them were written for Sendmail and will require some work to use with qmail.
5.2.1. qmail-pop3d
qmail-pop3d is the POP server included with qmail. It's a fine POP server, and many qmail sites use it. It's modular, and supports multiple authentication schemes via alternative authentication modules.
Note: qmail-pop3d supports only maildir-format mailboxes, so if you have users logging into the POP server and running MUA's locally, they all have to support maildir. If all of your users read mail via POP, the mailbox format on the server is not an issue.
<IP_ADDRESS>. Architecture of qmail-pop3d
A qmail-pop3d server consists of three modules:
- qmail-popup--gets username/password
- checkpassword--authenticates username/password
- qmail-pop3d--the POP daemon
Typically, qmail-popup is run via inetd or tcpserver, listening to port 110, the POP3 port. When a connection is made, it prompts for the username and password. Then it invokes checkpassword, which verifies the username/password and invokes qmail-pop3d if they match.
<IP_ADDRESS>. Installation of qmail-pop3d
1. Completely install and test qmail. If you want all users to have POPable mailboxes, make sure defaultdelivery is set to ./Maildir/. If you installed the /var/qmail/rc script from the Installation section, this is configured in control/defaultdelivery. If not, it's probably in /var/qmail/rc on the qmail-start command line.
2. Download a checkpassword program from http://www.qmail.org/top.html#checkpassword. The standard checkpassword, http://cr.yp.to/checkpwd.html, is a good choice if you don't need anything fancy.
3. Compile and install checkpassword according to the directions. Make sure you install it as /bin/checkpassword.
Note: If you install the standard checkpassword, don't forget to apply the errno patch after unpacking the source:
patch < /usr/local/src/netqmail-1.06/other-patches/checkpassword-0.90.errno.patch
4. mkdir /var/qmail/supervise/qmail-pop3d
5. Create a /var/qmail/supervise/qmail-pop3d/run script containing:
#!/bin/sh exec /usr/local/bin/softlimit -m 2000000 \ /usr/local/bin/tcpserver -v -R -H -l 0 0 110 /var/qmail/bin/qmail-popup \ FQDN /bin/checkpassword /var/qmail/bin/qmail-pop3d Maildir 2>&1
where FQDN is the fully qualified domain name of the POP server you're setting up, e.g., pop.example.net.
Note: The memory limit specified in the softlimit command may need to be raised depending upon your operating system and hardware platform. If attempts to connect to port 110 fail or POP3 connections fail mysteriously, or you see a message like:
/usr/local/bin/tcpserver: error while loading shared libraries: libc.so.6: failed to map segment from shared object: Cannot allocate memory
try raising it to 3000000 or 5000000.
6. mkdir /var/qmail/supervise/qmail-pop3d/log
7. Create a /var/qmail/supervise/qmail-pop3d/log/run script containing:
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t \ /var/log/qmail/pop3d
8. Set up the log directory and permissions on the run scripts, and link the service into /service:
chmod +t /var/qmail/supervise/qmail-pop3d # if daemontools < 0.75 mkdir /var/log/qmail/pop3d chown qmaill /var/log/qmail/pop3d chmod 755 /var/qmail/supervise/qmail-pop3d/run chmod 755 /var/qmail/supervise/qmail-pop3d/log/run ln -s /var/qmail/supervise/qmail-pop3d /service
9. Add the following to qmailctl's "start" section:
if svok /service/qmail-pop3d ; then svc -u /service/qmail-pop3d /service/qmail-pop3d/log else echo qmail-pop3d supervise not running fi
10. Add the following to qmailctl's "stop" section:
echo " qmail-pop3d" svc -d /service/qmail-pop3d /service/qmail-pop3d/log
11. Add the following to qmailctl's "stat" section:
svstat /service/qmail-pop3d svstat /service/qmail-pop3d/log
12. Add the following to qmailctl's "pause" section:
echo "Pausing qmail-pop3d" svc -p /service/qmail-pop3d
13. Add the following to qmailctl's "cont" section:
echo "Continuing qmail-pop3d" svc -c /service/qmail-pop3d
14. Add the following to qmailctl's "restart" section:
echo "* Restarting qmail-pop3d." svc -t /service/qmail-pop3d /service/qmail-pop3d/log
5.2.2. Qpopper
If you need a POP daemon that works with mbox-format mailboxes, you can use Qualcomm's Qpopper. Qpopper is available from http://www.eudora.com/products/unsupported/qpopper/.
5.2.3. Binc IMAP
Andreas Hanssen has written the Binc IMAP server. Binc IMAP is designed to use the same authentication mechanism (checkpassword) that qmail-pop3d uses, so it's a good fit for qmail servers. Like qmail-pop3d, it supports only Maildir mailboxes. See: http://www.bincimap.org/.
5.2.4. Dovecot
Timo Sirainen has written Dovecot, a IMAP and POP server that supports both mbox and maildir mailboxes. It was designed to be secure. It's available from http://www.dovecot.org/.
5.2.5. imap-maildir
David R. Harris has cleaned up the patch that adds maildir support to the University of Washington IMAP server and documented the installation process. See http://www.davideous.com/imap-maildir/.
5.2.6. Courier-IMAP
Sam Varshavchik has written an IMAP server that supports maildir mailboxes only. It's available from http://www.courier-mta.org/imap/.
5.2.7. Cyrus
Carnegie Mellon University's Project Cyrus includes an IMAP server. It's available from http://asg.web.cmu.edu/cyrus/imapd/. Rick Updegrove has written a qmail2cyrus wrapper for delivering messages to a Cyrus mail store. This wrapper is available from http://msgs.securepoint.com/cgi-bin/get/qmail0308/41/1/1.html.
5.3. POP and IMAP clients
5.3.1. fetchmail
fetchmail is a program that retrieves mail from a POP or IMAP server and re-injects it locally. fetchmail has no trouble retrieving mail from qmail servers, but there are a couple tricks for making it work well on a qmail client.
Here's a sample .fetchmailrc for a user on a qmail system:
poll mail.example.net proto pop3 nodns user dsill with password flubgart is dave here fetchall forcecr
This instructs fetchmail to connect to mail.example.net via POP3, log in as user dsill, password flubgart, retrieve all messages, and deliver them to dave@localhost. The forcecr causes fetchmail to end each line with a carriage return when injecting the message on the local system via SMTP. qmail requires this.
5.3.2. getmail
getmail is a program that retrieves mail from a POP server and delivers it to a maildir mailbox. It's actually a Python script, so you may need to install the Python interpreter before you can use getmail
getmail was written by Charles Cazabon, who maintains a web page for it at http://pyropus.ca/software/getmail/.
5.4. Multi-RCPT vs. Single RCPT delivery
Say you're an MTA, and one of your users sends a message to three people on hostx.example.com. There are several ways you could do this.
- You could open an SMTP connection to hostx, send a copy of the message to the first user, send a copy to the second user, send a copy to the third user, then close the connection.
- You could start three processes, each of which opens an SMTP connection to hostx, sends a copy of the message to one of the users, then closes the connection.
- You could open an SMTP connection to host, send a copy of the message addressed to all three users, then close the connection.
The first method is clearly inferior to the third. Even if the message is tiny, it'll take at least as long. And if the message is large, it'll take a lot longer and use more network bandwidth.
So scratch that one.
The second and third methods are a little more interesting.
The third method only opens one connection to hostx, and only sends one copy of the message. That makes for efficient use of bandwidth.
The second method uses multiple connections and sends multiple copies of the message. That "wastes" bandwidth, but due to the nature of the SMTP protocol, requires fewer round-trip delays, and is faster than the third method. It's also simpler than the third method, so the MTA can be coded in a more straightforward manner. And finally, because each recipient gets their own copy of the message, it's possible for the MTA to implement VERPs (see next section).
qmail always uses the second method (single RCPT). There are no patches to implement the third method (multiple RCPT)--it would require major work.
Although there are pathological cases where it can be slower than multiple RCPT, the simplicity and VERP advantages outweigh that overall.
Single RCPT delivery does use more bandwidth than multiple RCPT delivery, but the difference is often exaggerated. Most messages have, at most, a couple recipients, and they're usually on separate hosts, so multi-RCPT delivery buys them nothing. Even on a list server, where multi-RCPT delivery could help, the potential gains are small because SMTP uses only a fraction of the bandwidth over most links--HTTP usually gets the lion's share.
For example, if 10% of your uplink's bandwidth goes to SMTP, and your SMTP bandwidth could be reduced by, say, 25%, by using multi-RCPT delivery, that would only drop your SMTP bandwidth to 7.5%.
5.5. VERP
When a message is undeliverable, the MTA responsible is supposed to return a bounce message to the envelope return path (ERP). The bounce message should include the address of the recipient, the reason the message is undeliverable, and whether the problem is temporary or permanent. Some MTA's don't do the right thing, though. They might send the bounce to the address in the From header field, or the bounce might not identify the recipient.
For most user-to-user messages, these problems aren't too bad. One can usually figure things out based on the timing of the bounce or the contents. For mailing lists, the problem of bad bounces is more serious. Subscribers move, forwarding mail to their new address. If the new address starts having delivery problems, it can be impossible to tell which subscriber's mail is bouncing if the bounce message only includes the new address.
Dan Bernstein came up with a solution to this problem called VERP (Variable Envelope Return Path). Using VERPs, each message sent to each subscriber to a list has a unique return path. This allows a bounce handler to identify the problem subscriber.
For example, a typical non-VERP'ed mailing list has a return address of the form listname-owner@domain. For a VERP'ed list, the return address would look like listname-owner-subscriber=sdomain@ldomain, where the subscriber's address, subscriber@sdomain, is embedded between the "owner" and the "@". (The "@" in the subscriber's address is replaced with an "=".)
The ezmlm list manager uses VERPs to automatically handle bounces. It even provides subscribers with temporary delivery problems with a list of the messages they missed so they can retrieve them from the archive.
Russell Nelson wrote a bounce manager for Majordomo under qmail, but he no longer maintains it. It's available from http://www.qmail.org/bounceman-0.4.shar.
5.6. Troubleshooting
5.6.1. Processes
A properly-running, complete, but minimal qmail installation should always have the following four processes:
- qmail-send running as user qmails
- qmail-clean running as user qmailq
- qmail-rspawn running as user qmailr
- qmail-lspawn running as user root
Depending upon your flavor of UNIX, one of the following two commands should list these processes, and possibly a few more:
ps -ef | grep qmail ps waux | grep qmail
For example:
[dave@sparge dave]$ ps waux|grep qmail dave 2222 0.0 0.8 836 348 p4 S 10:25 0:00 grep qmail qmaild 351 0.0 1.0 840 400 ? S N 12:43 0:00 /usr/local/bin/tcpserver -v -x /etc/tcp.smtp.cdb -u 49491 -g 31314 0 smtp /var/qmail/bin/qmail-smtpd- qmaild 2220 0.0 1.0 844 420 ? S N 10:25 0:00 /usr/local/bin/tcpserver -v -x /etc/tcp.smtp.cdb -u 49491 -g 31314 0 smtp /var/qmail/bin/qmail-smtpd- qmaill 365 0.0 0.8 748 344 ? S N 12:43 0:00 splogger qmail qmailq 368 0.0 0.7 736 292 ? S N 12:43 0:00 qmail-clean qmailr 367 0.0 0.6 732 272 ? S N 12:43 0:00 qmail-rspawn qmails 350 0.0 0.8 776 336 ? S N 12:43 0:00 qmail-send root 340 0.0 0.6 724 252 ? S N 12:43 0:00 /usr/local/sbin/supervise /var/supervise/qmail-send /var/qmail/rc root 341 0.0 0.6 724 252 ? S N 12:43 0:00 /usr/local/sbin/supervise /var/supervise/tcpserver-qmail /usr/local/bin/tcpserver -v -x /etc/tcp.smtp root 366 0.0 0.7 736 276 ? S N 12:43 0:00 qmail-lspawn ./Mailbox [dave@sparge dave]$
If you run qmail or qmail-smtpd under supervise, as in the example above, you should see those processes as well. And if run qmail-smtpd under tcpserver, you should see a parent tcpserver process plus an additional tcpserver process for each active incoming SMTP connection.
If you use splogger (or multilog or cyclog) to handle logging, you'll have a splogger (or multilog or cyclog) process or two running as user qmaill.
Also, if qmail is busy delivering messages locally or remotely, you'll see up to concurrencylocal qmail-local processes and up to concurrencyremote qmail-remote processes.
5.6.2. Logs
<IP_ADDRESS>. multilog
multilog, which is part of the daemontools package, logs messages to a series of files in a specified directory.
The log directory is specified on the multilog command line, so you can find it by examining your qmail startup scripts.
The number of files in the log directory, and the maximum size of each file, are determined by multilog options. The log file names are the TAI (Temps Atomique International) timestamps of the time at which the file was started. The tai64nlocal command, also from daemontools, converts TAI timestamps into local, human-readable timestamps.
A typical multilog log entry looks like:
@4000000038c3eeb104a6ecf4 delivery 153: success: did_1+0+0/
"@4000000038c3eeb104a6ecf4" is the optional, but recommended, TAI timestamp. "delivery 153: success: did_1+0+0/" is the log message itself.
<IP_ADDRESS>. splogger
splogger uses the syslog logging system to timestamp messages and send them to the syslog daemon. Syslog is configured in /etc/syslog.conf. Messages sent to syslog have a facility and priority. Entries in /etc/syslog.conf filter on the facility and priority to direct the messages to the desired log file, remote log host, or the console. splogger logs to the mail facility, by default, so grep'ing the syslog.conf file for "mail" should show the disposition of qmail's log messages.
Typical locations include:
- /var/log/syslog
- /var/adm/SYSLOG
- /var/log/maillog
A typical syslog log entry looks like:
Jun 3 11:35:23 sparge qmail: 928424123.963558 delivery 153: success: did_1+0+0/
"Jun 3 11:35:23" is the syslog timestamp.
"sparge" is the name of the system that sent the message.
"qmail:" is the tag splogger places on all qmail log entries.
"928424123.963558" is an optional TAI timestamp (see next section).
"delivery 153: success: did_1+0+0/" is the log message itself.
<IP_ADDRESS>. Log messages
Here's a typical log sequence for a message sent to a remote system from the local system:
1 @4000000038c3eeb027f41c7c new msg 93869 2 @4000000038c3eeb027f6b0a4 info msg 93869: bytes 2343 from<EMAIL_ADDRESS>qp 18695 uid 49491 3 @4000000038c3eeb02877ee94 starting delivery 2392: msg 93869 to remote<EMAIL_ADDRESS>4 @4000000038c3eeb0287b55ac status: local 0/10 remote 1/20 5 @4000000038c3eeb104a13804 delivery 2392: success: <IP_ADDRESS>_accepted_message. /Remote_host_said:_250_CAA01516_Message_accepted_for_delivery/ 6 @4000000038c3eeb104a4492c status: local 0/10 remote 0/20 7 @4000000038c3eeb104a6ecf4 end msg 93869
Line 1 indicates that qmail has received a new message, and its queue ID is 93869. The queue ID is the i-node number of the /var/qmail/queue/mess/NN/ file--the queue file that contains the message. The queue ID is guaranteed to be unique as long as the message remains in the queue.
Line 2 says that the message is from<EMAIL_ADDRESS>and is 2343 bytes.
Line 3 says qmail-remote is starting to deliver the message to<EMAIL_ADDRESS>and it's assigning the ID 2392 to the delivery.
Line 4 says 0 local deliveries and 1 remote delivery are pending.
Line 5 says delivery 2392 is complete and successful, and it returns the remote server's response, which often contains information the remote mail administrator would find helpful in tracking a delivery. In this case, the "CAA01516" is the remote system's delivery ID.
Line 6 says 0 local deliveries and 0 remote deliveries are pending, i.e., the delivery is complete.
Line 7 says that the message has been delivered completely and removed from the queue. At this point, the queue ID, 93869, is reusable for another delivery.
5.7. Big Servers
See also qmail-ldap.
5.7.1. Scalable parallelism
Use a fast NFS network file server to store user directories. Set up multiple equal-preference SMTP servers delivering to maildir mailboxes on the file server.
5.8. Migrating from Sendmail to qmail
Check Dan Bernstein's Sendmail->qmail page at http://cr.yp.to/qmail/sendmail.html.
5.9. Mailing List Managers
Mailing list managers (MLM's) are systems that help list owners run mailing lists. Their duties fall into two main divisions: managing the lists of subscribers, and controlling the resending of messages to the subscribers.
Most (all?) UNIX mailing list managers can be made to work with qmail.
5.9.1. ezmlm
ezmlm was written by Dan Bernstein, the author of qmail. It was written for use with qmail, and relies on several features of qmail. Most notably, it uses VERPs to reliably process bounce messages. ezmlm is somewhat unique among MLM's in that it doesn't process commands sent to a central MLM address: it appends the command to the name of the list. E.g., to subscribe to the<EMAIL_ADDRESS>list, one sends a message to<EMAIL_ADDRESS>For more information about ezmlm, see http://www.ezmlm.org/, the unofficial ezmlm web site, and the official home of ezmlm-idx, a very nice add-on that includes many useful features.
5.9.2. Majordomo
Majordomo is one of the most popular UNIX MLMs. It works fine with qmail provided a few simple changes are made. Russ Allbery has written a FAQ about qmail/Majordomo available from http://web.archive.org/web/20050308091420/http://www.eyrie.org/~eagle/faqs/mjqmail.html.
5.10. Patches
Various source code patches are available for qmail. To install a patch, download it, cd to the qmail source tree, and apply it using the patch command.
cd /usr/local/src/qmail/qmail-1.03 patch -p0 </tmp/patchfile
Note: See the patch man page for more information. This is just an example. Also, you might need to use a current version of GNU patch to successfully apply some patches. See http://www.gnu.org/software/patch/patch.html.
Stop qmail by killing qmail-send or, if you installed the qmailctl script in the Installation section, do:
qmailctl stop
Then rebuild and install the new binaries:
make setup check
And restart qmail:
qmailctl start
Finally, test qmail--especially the part you patched.
Note: Although http://www.qmail.org/ lists many patches for qmail, none of the them have been approved by the author of qmail. They may introduce security, reliability, efficiency, or functionality problems not present in qmail. Most qmail installations only require the some of the Recommended patches. You should not install any patches that you don't clearly require.
5.10.1. Recommended Patches
qmail.org has a "Recommended Patches" section: http://qmail.org/top.html#patches. These patches address the few known bugs in qmail.
Note: all of the Recommended Patches have been included in the netqmail distribution. See http://www.qmail.org/netqmail/.
<IP_ADDRESS>. errno.h patches
This patch fixes a problem with missing errno.h inclusions. See http://article.gmane.org/gmane.mail.qmail.general/13960 for a detailed explanation and the patch itself.
Mate Wierdl has errno.h patches for all of Dan Bernstein's software including qmail, daemontools, and ucspi-tcp. These patches are available from http://www.thedjbway.org/patches/djb_errno_patches.tgz.
<IP_ADDRESS>. qmail-local TAB patch
This patch fixes a minor bug in the parsing of .qmail files that start with TAB characters. http://www.ornl.gov/lists/mailing-lists/qmail/2000/10/msg00696.html
<IP_ADDRESS>. IP <IP_ADDRESS> patch
This patch causes the IP address <IP_ADDRESS> to be recognized as local. http://www.suspectclass.com/~sgifford/qmail/qmail-<IP_ADDRESS>.patch
5.10.2. DNS
Historically, DNS responses have been limited to 512 bytes. Some large sites have started returning MX responses longer than that. qmail and many other programs have a problem with Domain Name Server (DNS) queries that return very large results. There are two ways to fix this in qmail and one workaround that might be sufficient for some applications.
<IP_ADDRESS>. Christopher K. Davis' patch, http://www.ckdhr.com/ckd/qmail-103.patch
This is an adaptation of a patch by Chuck Foster that should work with any resolver library, no matter how old, and uses a guard byte to avoid the "number of bytes placed in the buffer" library bug. It reallocates only once, to 65536, rather than just to the size needed, so it can be less memory-efficient than Chuck's patch (though, like his patch, it only reallocates if the response is larger than PACKETSZ, which defaults to 512 bytes). After reallocating, it forces a TCP query, rather than requiring the resolver library to do so (avoiding an extra round-trip between qmail and the name server, though if they're on the same machine or local network this is not a big worry).
<IP_ADDRESS>. Bump the packet buffer size up to 65536
Works with recent BIND resolver libraries, which will automatically do a TCP query within the library code if the reply comes back with the truncation bit set. This is the simplest fix, though it's also potentially the most wasteful of memory, depending on how your system handles paging. To do this, just replace PACKETSZ with 65536 in dns.c and rebuild qmail.
<IP_ADDRESS>. Run dnscache from djbdns
dnscache is, as the name implies, a caching DNS server. It knows how to handle large DNS responses and removes unnecessary information from them, so the response it returns is usually much smaller than the direct response. It also generally improves DNS lookup performance for all services that use DNS. Because it doesn't require patching qmail, this might be an acceptable workaround. Unfortunately, it's not a complete fix because responses can still be too large for qmail. See the djbdns section under Related Packages for more information.
5.10.3. qmail-ldap
This patch, by Andre Oppermann, et al, implements Lightweight Directory Access Protocol (LDAP) support in qmail. LDAP is like a network phone book. Using qmail-ldap, it should be possible for a POP server to serve many thousands of users. See http://www.nrg4u.com/.
5.11. QMTP
QMTP is the Quick Mail Transfer Protocol, an SMTP replacement protocol designed by Dan Bernstein. The protocol is defined at http://cr.yp.to/proto/qmtp.txt. QMTP is similar to SMTP, but is simpler, faster, and incompatible with SMTP. qmail includes a QMTP server, qmail-qmtpd, which is run very much like qmail-smtpd. QMTP usually uses port 209.
qmail doesn't include a QMTP client, but the serialmail package does. maildirqmtp takes a maildir mailbox and delivers the messages it contains to designated QMTP server via QMTP.
QMTP is not a drop-in replacement for SMTP, and is not yet in widespread use across the Internet.
Russ Nelson has a patch for qmail-remote that supports QMTP. It's available from http://www.qmail.org/qmail-1.03-qmtpc.patch. He also has a tarball that can be extracted in /service to enable a QMTP service. It's available from http://www.qmail.org/qmtpd-service.tar.gz.
5.12. Rejecting Invalid Recipients During SMTP Dialogue
When a remote server connects to qmail-smtpd and offers it a message, qmail-smtpd checks the recipient addresses against the contents of control/rcpthosts. If the host or domain after the @ symbol is listed in control/rcpthosts, qmail-smtpd accepts the message, it's placed in the queue, and qmail-send attempts delivery. If the local recipient is invalid--there's no user or alias by that name--qmail-send generates a bounce message and sends it to the return address specified during the SMTP dialogue.
In a well-behaved world, either strategy would be fine. Unfortunately, there are a lot of poorly-behaved spammers out there. Some will attempt to deliver messages to recipients that "might" exist on your server--using a database of common names, a dictionary, or even a generated list of all possible alphanumeric strings.

Some MTAs validate the local recipient during the SMTP dialogue and refuse to accept the message if the recipient is invalid. This saves the server from a lot of unnecessary work, but has a negative side effect, too. Using this validation, spammers can quickly determine which addresses are valid.
There are several ways to implement recipient validation during the SMTP dialogue with qmail. Eben Pratt has assembled a list of them at http://netdevice.com/qmail/rcptck/. Most of these solutions require maintaining a database of valid or invalid recipients or patterns. One that doesn't is Paul Jarc's qmail-realrcptto, available from http://code.dogmap.org./qmail/.
5.13. TLS and STARTTLS
Scott Gifford has written a very thorough and detailed step-by-step guide to using transport layer security (TLS) with qmail. The guide covers STARTTLS for SMTP and STLS for POP3D specifically for netqmail. It's available at http://www.suspectclass.com/~sgifford/ucspi-tls/ucspi-tls-qmail-howto.html.
A. Acknowledgments
First, thanks to Dan Bernstein for designing and writing such a powerful and elegant system. After nearly ten years of use, qmail still impresses me.
I'd also like to thank the members of the qmail mailing list. Two members deserve special mention. The first is Russ Nelson, one of the most helpful, patient, knowledgeable, and funny contributors. His contributions to the qmail community are second only to DJB's. The second is Charles Cazabon, who's close on Russ' heels. Charles is currently the major contributor to the mailing list, answering more questions correctly than anyone else. Charles has also written a couple of very useful utilities, getmail and pymsgauth, and was technical editor for The qmail Handbook where his contributions were critical to the success of the book, and for which he has received too little reward and recognition.
Thanks also to everyone who reviewed or contributed to this document, including:
- Vince Vielhaber
- Chris Green
- Christopher K. Davis
- Scott Schwartz
- Fred Lindberg
- Russell P. Sutherland
- Alex Miller
- Tim Hunter
- Frank D. Cringle
- Mahlon Smith
- Rogerio Brito
- Tony Hansmann
- Matthias Andree
- Tillman Hodgson
- Stefan Witzel
- Scott Gifford
- too many others to mention...
Special thanks to Henning Brauer for donating the lifewithqmail.org domain and hosting it!
Special thanks also to Michael M. Kadrie of ATLAS Design Group, http://www.atlasdesigngroup.com, for the nifty new qmail logo!
Life with qmail was written using Simple Document Format (SDF), a very cool Perl-based markup language that generates HTML, plain text, PostScript, POD, and other formats. It made the job much easier. See http://search.cpan.org/author/IANC/sdf-2.001/ for more information.
B. Related Packages
B.1. dot-forward
Sendmail uses .forward files, pronounced dot forward, to allow users to control the delivery of messages they receive. qmail uses a similar mechanism: .qmail files. The dot-forward package gives qmail the ability to use .forward files. Systems running Sendmail or any other MTA that uses .forward files might want to consider using dot-forward to avoid having to convert existing .forward files to their .qmail equivalents--or simply to make the transition to qmail less visible to their users.
dot-forward is a small package: easy to install and configure. The source is available from http://cr.yp.to/software/dot-forward-0.71.tar.gz.
dot-forward was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/dot-forward.html.
B.2. fastforward
fastforward is another Sendmail compatibility add-on. Sendmail uses a central alias database kept in a single file, usually /etc/aliases. qmail uses a series of dot-qmail files in /var/qmail/alias, one file per alias. If you're migrating to qmail, and you've got a Sendmail-format aliases file you don't want to convert, fastforward gives qmail the ability to use the aliases file as-is.
The source is available from http://cr.yp.to/software/fastforward-0.51.tar.gz.
fastforward was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/fastforward.html.
B.3. ucspi-tcp
qmail's SMTP server doesn't run as a stand alone daemon. A helper program such as inetd, xinetd, or tcpserver runs as a daemon. When it receives a TCP connection to port 25, the SMTP port, it executes a copy of qmail-smtpd.
Inetd is the standard network server "super-server". It can be configured through /etc/inetd.conf to run qmail-smtpd, but the recommended tool is tcpserver, which is part of the ucspi-tcp package. ucspi-tcp is an acronym for UNIX Client-Server Program Interface for TCP, and it's pronounced ooks-pie tee see pee.
tcpserver is preferred over inetd because:
- tcpserver allows one to limit the number of simultaneous connections to a service. Inetd has a connection-rate limiting mechanism that temporarily disables services that are "too" busy.
- tcpserver can be configured to deny access to certain hosts or to recognize local hosts and flag them so qmail-smtpd can treat them differently.
- tcpserver is the only server supported by the author of qmail.
The source is available from http://cr.yp.to/ucspi-tcp/ucspi-tcp-0.88.tar.gz.
Gerrit Pape distributes the documentation for ucspi-tcp as man pages from http://smarden.org/pape/djb/.
ucspi-tcp was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/ucspi-tcp.html.
B.4. daemontools
The daemontools package contains a set of utilities for controlling and monitoring services. It's not mandatory, but it's highly recommended, especially for busy systems. It includes:
- supervise, which monitors a service and restarts it if it dies.
- svc, which talks to supervise and allows one to stop, pause, or restart the service.
- multilog, which maintains a log for a service, automatically rotating it to keep it under the configured size.
- setuidgid, which runs programs for the superuser with a normal user's UID and GID.
The source for daemontools is available from: http://cr.yp.to/daemontools/daemontools-0.76.tar.gz.
Gerrit Pape distributes the documentation for daemontools as man pages from http://smarden.org/pape/djb/.
daemontools was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/daemontools.html.
B.5. qmailanalog
qmailanalog processes qmail's log file and produces a series of reports that tell one how much and what kind of work the system is doing. If you need statistics about how many messages are being sent or received, how big they are, and how quickly they're being processed, qmailanalog is what you need.
As a bonus, the matchup program combines qmail's multiple log lines per delivery into one--not unlike the familiar Sendmail logs.
The source for qmailanalog is available from http://cr.yp.to/software/qmailanalog-0.70.tar.gz.
qmailanalog was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/qmailanalog.html.
Note: qmailanalog relies on log entry timestamps in the fractional second format used by accustamp. In order to use it with logs generated by multilog, which are in TAI64N format, you'll need to translate them into the old format. One program to do that is available from http://www.qmail.org/tai64nfrac.
B.6. rblsmtpd
If you've never been spammed, consider yourself very lucky. Most e-mail users are all too familiar with Unsolicited Bulk E-mail (UBE), aka "spam". Most of it is advertisements for sex sites, chain letters, and other scams. Back in the days of old, up until around 1998 or so, most MTA's on the Internet were open relays, i.e., they would accept mail from anyone for anyone, even if neither sender nor recipient was local. Spammers use open relays, if they can find any, to deliver their spam. It covers their tracks, redirects the backlash toward the "innocent" relay site, and saves them lots of CPU time and network bandwidth.
Such open relays are considered very bad form these days, and several anti-spam vigilante groups have created a mechanism for identifying open relays and other common sources of spam so they can avoid accepting SMTP connections from them.
rblsmtpd is an RBL SMTP Daemon. It sits between tcpserver and qmail-smtpd and rejects connections from systems identified on one of these lists.
For example, to run rblsmtpd under tcpserver, try something like:
#!/bin/sh QMAILDUID=`id -u qmaild` NOFILESGID=`id -g qmaild` MAXSMTPD=`cat /var/qmail/control/concurrencyincoming` exec /usr/local/bin/softlimit -m 2000000 \ /usr/local/bin/tcpserver -v -R -H -l 0 -x /etc/tcp.smtp.cdb -c "$MAXSMTPD" \ -u "$QMAILDUID" -g "$NOFILESGID" 0 smtp /usr/local/bin/rblsmtpd\ -r relays.ordb.org /var/qmail/bin/qmail-smtpd 2>&1
rblsmtpd was previously available as a separate utility, but is now bundled with ucspi-tcp.
rblsmtpd was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/ucspi-tcp/rblsmtpd.html.
Charles Cazabon has a patch that removes the default RBL hardcoded into rblsmtpd since it's no longer free. The patch is available from http://pyropus.ca/software/misc/rblsmtpd-nodefaultrbl.patch.
B.7. serialmail
qmail was designed for systems with full time, high speed connectivity. serialmail is a set of tools that make qmail better suited to intermittent, low speed connectivity. With serialmail on such a system, qmail is configured to deliver all remote mail to a single maildir. The serialmail maildirsmtp command is used to upload the maildir to the ISP's mail hub when the connection is brought up. If the ISP supports QMTP (see QMTP under Advanced Topics), maildirqmtp can also be used.
serialmail can be used on the ISP side of the connection to implement AutoTURN: an SMTP connection by a client causes the server to initiate a connection back to the client for sending messages queued on the server for the client. This is similar to the ETRN SMTP function.
The source for serialmail is available from http://cr.yp.to/software/serialmail-0.75.tar.gz.
serialmail was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/serialmail.html.
B.8. mess822
mess822 is a library and set of applications for parsing RFC 822 compliant mail messages. The applications include:
- ofmipd: a daemon that accepts messages from clients and rewrites From fields based on a database.
- new-inject: a qmail-inject replacement that supports user-controlled hostname rewriting.
- iftocc: a .qmail utility for checking whether a message was sent to a specific address.
- 822header, 822field, 822date, and 822received: extract information from a message.
- 822print: pretty-prints a message.
The source for mess822 is available from http://cr.yp.to/software/mess822-0.58.tar.gz.
mess822 was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/mess822.html.
B.9. ezmlm
ezmlm is a high performance, easy-to-use mailing list manager (MLM) for qmail. If you're familiar with LISTSERV or Majordomo, you know what a mailing list manager does. For more information about mailing lists under qmail see Mailing List Managers under Advanced Topics.
The source for ezmlm is available from http://cr.yp.to/software/ezmlm-0.53.tar.gz.
ezmlm was written by Dan Bernstein, who maintains a web page for it at http://cr.yp.to/ezmlm.html.
Fred Lindberg and Fred B. Ringel have developed an extension to ezmlm called ezmlm-idx. It adds lots of useful features and is highly recommended. It's now being maintained by Bruce Guenter available from http://www.ezmlm.org/.
B.10. safecat
safecat reliably writes a file into a maildir mailbox. It is particularly useful for filing messages in procmail recipes. For example, the following recipe files all messages in Maildir:
:0w |safecat Maildir/tmp Maildir/new
safecat was written by Len Budney, who maintains a web page for it at http://jeenyus.net/~budney/linux/software/safecat.html.
B.11. djbdns
djbdns is a DNS server written by the author of qmail. It includes tinydns, a DNS content server, and dnscache, a caching DNS server.
The official web page for djbdns is http://cr.yp.to/djbdns.html.
B.12. maildrop
maildrop is a mail filter similar to procmail.
maildrop was written by Sam Varshavchik, who maintains a web page for it at http://www.courier-mta.org/maildrop/.
B.13. syncdir
syncdir is small library that makes the link() system call synchronous. This is necessary when using qmail with the queue on a filesystem that doesn't perform link() synchronously, such as Linux's ext2fs, Reiserfs, SGI's XFS, and BSD FFS with softupdates.
syncdir was written br Bruce Guenter and is available from http://untroubled.org/syncdir/. Installation instructions are available from http://www.ornl.gov/lists/mailing-lists/qmail/2001/12/msg00949.html.
C. How Internet Mail Works
C.1. How a message gets from point A to point B
When a user on one host sends a message to a user on a another host, many things happen behind the scenes that you may not be aware of.
Let's say Alice<EMAIL_ADDRESS>wants to send a message to Bob<EMAIL_ADDRESS>Here's what happens:
1. Alice composes the message with her mail user agent (MUA), something like mutt or pine. She specifies the recipient in a To field, the subject of the message in a Subject field, and the text of the message itself. It looks something like:
To: bob@beta Subject: lunch How about pizza?
2. When she's satisfied with the message, she tells the MUA to send it.
3. At this point, the MUA can add additional header fields like Date and Message-Id and modify the values Alice entered (e.g., replace bob@beta with "Bob<EMAIL_ADDRESS>Next, the MUA injects the message into the mail system. There are two ways to this: it can run a program provided by the mail system for the purpose of injecting messages, or it can open a connection to the Simple Mail Transfer Protocol (SMTP) port on either the local system or a remote mail server. For this example, we'll assume the MUA uses a local injection program to pass messages to the MTA. The details of the injection process vary by MTA, but on UNIX systems the sendmail method is a de facto standard. With this method, the MUA can put the header and body in a file, separated by a blank line, and pass the file to the sendmail program.
4. If the injection succeeds--the message was syntactically correct and sendmail was invoked properly--the message is now the MTA's responsibility. Details vary greatly by MTA, but generally the MTA on alpha examines the header to determine where to send the message, opens an SMTP connection to beta, and forwards the message to the MTA on the beta system. The SMTP dialogue requires messages to be sent in two parts: the envelope, which specifies the recipient's address<EMAIL_ADDRESS>and the return address (alice@alpha.example.com), and the message itself, which consists of the header and body.
5. If the beta MTA rejects the message, perhaps because there's no user bob on the system, the MTA on alpha sends a bounce message to the return address, alice@alpha, to notify her of the problem.
6. If the beta MTA accepts the message, it looks at the recipient's address, determines whether it's local to beta or on a remote system. In this case, it's local, so the MTA either delivers the message itself or passes it to a mail delivery agent (MDA) like /bin/mail or procmail.
7. If the delivery fails, perhaps because Bob has exceeded his mail quota, the beta MTA sends a bounce message to the envelope return address, alice@alpha.
8. If the delivery succeeds, the message waits in Bob's mailbox until his MUA reads it and displays it.
C.2. More information
For information about how Internet mail works, see one or more of the following:
- Internet mail, by the author of qmail. http://cr.yp.to/im.html
- SMTP, by the author of qmail. http://cr.yp.to/smtp.html
- Internet mail message header format, by the author of qmail. http://cr.yp.to/immhf.html
C.2.1. Internet RFC's
Internet Requests for Comment (RFC's) are the official documentation of the Internet. Most of these are well beyond the commentary stage, and define Internet protocols such as TCP, FTP, Telnet, and the various mail standards and protocols.
- RFC 821, Simple Mail Transfer Protocol (obsoleted by RFC 2821) http://www.ietf.org/rfc/rfc0821.txt
- RFC 822, Standard for the Format of ARPA Internet Text Messages (obsoleted by RFC 2822) http://www.ietf.org/rfc/rfc0822.txt
- RFC 931, Authentication Server. http://www.ietf.org/rfc/rfc0931.txt
- RFC 974, Mail Routing and the Domain System. http://www.ietf.org/rfc/rfc0974.txt
- RFC 1123, Requirements for Internet Hosts -- Application and Support. http://www.ietf.org/rfc/rfc1123.txt
- RFC 1413, Identification Protocol. http://www.ietf.org/rfc/rfc1413.txt
- RFC 1423, Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers. http://www.ietf.org/rfc/rfc1423.txt
- RFC 1651, SMTP Service Extensions. http://www.ietf.org/rfc/rfc1651.txt
- RFC 1652, SMTP Service Extension for 8bit-MIMEtransport. http://www.ietf.org/rfc/rfc1652.txt
- RFC 1806, Content disposition. header. http://www.ietf.org/rfc/rfc1806.txt
- RFC 1854, SMTP Service Extension for Command Pipelining. http://www.ietf.org/rfc/rfc1854.txt
- RFC 1891, SMTP Service Extension for Delivery Status Notifications. http://www.ietf.org/rfc/rfc1891.txt
- RFC 1892, The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages. http://www.ietf.org/rfc/rfc1892.txt
- RFC 1893, Enhanced mail system status codes. http://www.ietf.org/rfc/rfc1893.txt
- RFC 1894, An Extensible Message Format for Delivery Status Notifications. http://www.ietf.org/rfc/rfc1894.txt
- RFC 1939, Post Office Protocol - Version 3. http://www.ietf.org/rfc/rfc1939.txt
- RFC 1985, SMTP Service Extension for Remote Message Queue Starting (ETRN). http://www.ietf.org/rfc/rfc1985.txt
- RFC 1991, PGP Message Exchange Formats. http://www.ietf.org/rfc/rfc1991.txt
- RFC 2015, MIME Security with Pretty Good Privacy. (PGP). http://www.ietf.org/rfc/rfc2015.txt
- RFC 2045, MIME Internet message bodies. http://www.ietf.org/rfc/rfc2045.txt
- RFC 2046, MIME Media Types. http://www.ietf.org/rfc/rfc2046.txt
- RFC 2047, MIME Headers. http://www.ietf.org/rfc/rfc2047.txt
- RFC 2048, MIME Registration Procedures. http://www.ietf.org/rfc/rfc2048.txt
- RFC 2049, MIME Conformance Criteria. http://www.ietf.org/rfc/rfc2049.txt
- RFC 2142, Mailbox names for common services. http://www.ietf.org/rfc/rfc2142.txt
- RFC 2183, Content Disposition header. http://www.ietf.org/rfc/rfc2183.txt
- RFC 2821, Simple Mail Transfer Protocol. http://www.ietf.org/rfc/rfc2821.txt
- RFC 2822, Internet Message Format http://www.ietf.org/rfc/rfc2822.txt
A comprehensive list of mail-related RFC's is available from the Internet Mail Consortium at http://www.imc.org/mail-standards.html.
D. Architecture
D.1. Modular system architecture
Internet MTA's perform a variety of tasks. Earlier designs like Sendmail and smail are monolithic. In other words, they have one large, complex program that "switches hats": it puts on one hat to be an SMTP server, another to be an SMTP client, another to inject messages locally, another to manage the queue, etc.
qmail is modular. Each of these functions is performed by a separate program. As a result, the programs are much smaller, simpler, and less likely to contain functional or security bugs. To further enhance security, qmail's modules run with different privileges, and they don't "trust" each other: they don't assume the other modules always do only what they're supposed to do.
The core modules are:
| Modules | Function |
| qmail-smtpd | accepts/rejects messages via SMTP |
| qmail-inject | injects messages locally |
| qmail-rspawn/qmail-remote | handles remote deliveries |
| qmail-lspawn/qmail-local | handles local deliveries |
| qmail-send | processes the queue |
| qmail-clean | cleans the queue |
There's also a down side to the modular approach. Unlike a monolithic MTA, the interactions between modules are well-defined, and modules only exchange the minimum necessary information with each other. This is generally A Good Thing, but sometimes it makes it hard to do things. For example, the sendmail "-v" flag causes Sendmail to print a trace of its actions to standard output for debugging purposes. Since the one sendmail binary handles injection, queueing, alias processing, .forward file processing, and remote forwarding via SMTP, it is able to easily trace the entire delivery until the message is delivered. The equivalent capability in qmail doesn't exist, and would require substantial code changes and additional complexity to implement the passing of the "debug" flag from module to module.
D.2. File structure
/var/qmail is the root of the qmail file structure. This can be changed when qmail is being built, but it's a good idea to leave it unchanged so other administrators know where to find things. If you really want to relocate some or all of the qmail tree, it's better to do that using symbolic links. See the Create directories subsection of the Installation section for details.
The top-level subdirectories are:
| Directory | Contents |
| alias | .qmail files for system-wide aliases |
| bin | program binaries and scripts |
| boot | startup scripts |
| control | configuration files |
| doc | documentation (except man pages) |
| man | man pages |
| queue | the queue of unsent messages |
| users | the qmail-users database files |
D.3. Queue structure
The file INTERNALS in the build directory discusses the details of queueing more thoroughly. This is a broader overview of structure of the queue.
| Subdirectory | Contents |
| bounce | permanent delivery errors |
| info* | envelope sender addresses |
| intd | envelopes under construction by qmail-queue |
| local* | local envelope recipient addresses |
| lock | lock files |
| mess* | message files |
| pid | used by qmail-queue to acquire an i-node number |
| remote* | remote envelope recipient addresses |
| todo | complete envelopes |
Note: Directories marked with an "*" contain a series of split subdirectories named "0", "1", ..., up to (conf-split-1), where conf-split is a compile-time configuration setting contained in the file conf-split in the build directory. It defaults to 23. The purpose of splitting these directories is to reduce the number of files in a single directory on very busy servers. conf-split must be a prime number.
Files under the mess subdirectory are named after their i-node number. What this means is that you can't manually move them using standard UNIX utilities like mv, dump/restore, and tar. There are a couple user-contributed utilities on http://www.qmail.org/ that will rename queue files correctly.
Note: It is not safe to modify queue files while qmail is running. If you want to modify the queue, stop qmail first, play with the queue carefully, then restart qmail.
D.4. Pictures
There is a series of files in /var/qmail/doc with names starting with PIC. These are textual "pictures" of various situations that qmail handles. They show the flow of control through the various modules, and are very helpful for debugging and creating complex configurations.
| Filename | Scenario |
| PIC.local2alias | locally-injected message delivered to a local alias |
| PIC.local2ext | locally-injected message delivered to an extension address |
| PIC.local2local | locally-injected message delivered to a local user |
| PIC.local2rem | locally-injected message delivered to a remote address |
| PIC.local2virt | locally-injected message delivered to an address on a local virtual domain |
| PIC.nullclient | a message injected on a null client |
| PIC.relaybad | a failed attempt to use the local host as a relay |
| PIC.relaygood | a successful attempt to use the local host as a relay |
| PIC.rem2local | a message received via SMTP for a local user |
These files are also available on-line from:
If you want real pictures of qmail, check out Andre Opperman's "big qmail picture" at http://www.nrg4u.com/.
E. Infrequently Asked Questions
These are questions that don't qualify as frequently asked, but which are important and not easy to answer.
E.1. How frequently does qmail try to send deferred messages?
Each message has its own retry schedule. The longer a message remains undeliverable, the less frequently qmail tries to send it. The retry schedule is not configurable. The following table shows the retry schedule for a message that's undeliverable to a remote recipient until it bounces. Local messages use a similar, but more frequent, schedule.
| Delivery Attempt | Seconds | D-HH:MM:SS |
| 1 | 0 | 0-00:00:00 |
| 2 | 400 | 0-00:06:40 |
| 3 | 1600 | 0-00:26:40 |
| 4 | 3600 | 0-01:00:00 |
| 5 | 6400 | 0-01:46:40 |
| 6 | 10000 | 0-02:46:40 |
| 7 | 14400 | 0-04:00:00 |
| 8 | 19600 | 0-05:26:40 |
| 9 | 25600 | 0-07:06:40 |
| 10 | 32400 | 0-09:00:00 |
| 11 | 40000 | 0-11:06:40 |
| 12 | 48400 | 0-13:26:40 |
| 13 | 57600 | 0-16:00:00 |
| 14 | 67600 | 0-18:46:40 |
| 15 | 78400 | 0-21:46:40 |
| 16 | 90000 | 1-01:00:00 |
| 17 | 102400 | 1-04:26:40 |
| 18 | 115600 | 1-08:06:40 |
| 19 | 129600 | 1-12:00:00 |
| 20 | 144400 | 1-16:06:40 |
| 21 | 160000 | 1-20:26:40 |
| 22 | 176400 | 2-01:00:00 |
| 23 | 193600 | 2-05:46:40 |
| 24 | 211600 | 2-10:46:40 |
| 25 | 230400 | 2-16:00:00 |
| 26 | 250000 | 2-21:26:40 |
| 27 | 270400 | 3-03:06:40 |
| 28 | 291600 | 3-09:00:00 |
| 29 | 313600 | 3-15:06:40 |
| 30 | 336400 | 3-21:26:40 |
| 31 | 360000 | 4-04:00:00 |
| 32 | 384400 | 4-10:46:40 |
| 33 | 409600 | 4-17:46:40 |
| 34 | 435600 | 5-01:00:00 |
| 35 | 462400 | 5-08:26:40 |
| 36 | 490000 | 5-16:06:40 |
| 37 | 518400 | 6-00:00:00 |
| 38 | 547600 | 6-08:06:40 |
| 39 | 577600 | 6-16:26:40 |
| 40 | 608400 | 7-01:00:00 |
E.2. Why can't I send mail to a large site with lots of MX's?
If you're getting:
deferral: CNAME_lookup_failed_temporarily._(#4.4.3)/
The problem might be that qmail can't handle large name server query responses. The fix is to install a patch or workaround. See Patches under Advanced Topics.
There's also a question as to why some people don't have trouble reaching such systems. Basically, depending on the timing and ordering of queries made to your local nameserver, the size of the response to an ANY query for "aol.com" may be larger than the 512 byte limit of a UDP packet, or it may not.
"May not" is likely to happen if the A and MX records time out, but the NS records don't. Since the .COM servers set a 2 day TTL on those, but AOL sets a 1 hour TTL on their records, this will often happen on less busy nameservers. Busier nameservers are more likely to have those records in their cache at any given time, frustrating an unpatched qmail's attempts to check for CNAMEs.
A better test is to send mail to<EMAIL_ADDRESS>if it clears your queue and winds up bouncing from ckdhr.com, your MTA can send mail to hosts with MX lists that exceed 512 bytes. (By using a single RRset, with a single TTL, that exceeds 512 bytes, the problem can be seen without depending on the timing and ordering of other queries.)
E.3. What is QUEUE_EXTRA?
QUEUE_EXTRA is a compile-time configuration variable that specifies an additional recipient that will be added to every delivery. This is used primarily for logging. E.g., the FAQ describes how to use QUEUE_EXTRA to keep copies of all incoming and outgoing messages.
To use QUEUE_EXTRA, edit extra.h specifying the additional recipient in the format "Trecipient\0", and the length of the QUEUE_EXTRA string in QUEUE_EXTRALEN (the "\0" counts as one character). For example:
#define QUEUE_EXTRA "Tlog\0" #define QUEUE_EXTRALEN 5
Shut down qmail if it's running. If you installed the qmailctl script from the Installation section, that can be done by:
qmailctl stop
If you don't have the qmailctl script, you should use your startup/shutdown script or send qmail-send a TERM signal.
Then rebuild qmail using:
make setup check
Populate ~alias/.qmail-log with whatever logging you want. E.g., to log Message-ID's:
| awk '/^$/ { exit } /^[mM][eE][sS][sS][aA][gG][eE]-/ { print }'
Finally, restart qmail.
F. Error Messages
qmail error messages and what they mean.
See RFC 1893 for an explanation of the error codes in parentheses.
This appendix is incomplete.
G. Gotchas
These "gotchas" frequently cause problems for qmail newbies.
G.1. qmail doesn't deliver mail to superusers.
To prevent the possibility of qmail-local running commands as a privileged user, qmail ignores all users whose UID is 0. This is documented in the qmail-getpw man page.
That doesn't mean qmail won't deliver to root, it just means that such a delivery will have to be handled by a non-privileged user. Typically, one creates an alias for root by populating ~alias/.qmail-root.
G.2. qmail doesn't deliver mail to users who don't own their home directory.
Another security feature, and just good general practice. This is documented in the qmail-getpw man page.
G.3. qmail doesn't deliver mail to users whose usernames contain uppercase letters.
qmail converts the entire "local part"--everything left of the "@" in an address, to lowercase. The man page doesn't come out and say that, but the code does. The fact that it ignores users with uppercase characters is documented in the qmail-getpw man page.
G.4. qmail replaces dots (.) in extension addresses with colons (:).
Another security feature. The purpose is prevent extension addresses from backing up the file tree using "..". By replacing them with colons, qmail ensures that all .qmail files for a user are under their home directory. Documented in the dot-qmail man page.
G.5. qmail converts uppercase characters in extension addresses to lowercase.
This is another result of the fact that qmail lowercases the entire local part of addresses. Documented in the dot-qmail man page.
G.6. qmail doesn't use /etc/hosts.