Qmail, VMailMgr and Courier-IMAP are a very powerful and easy to use solution, but they are not what I would consider easy to setup. I hope this document helps with that.
Here is the authors (Dan Bernstein) blurb:
Qmail is a secure, reliable, efficient, simple message transfer agent. It is meant as a replacement for the entire sendmail-binmail system on typical Internet-connected UNIX hosts.
It offers POP3, and IMAP (with the help of Courier-IMAP) so that you can use any mail client you prefer.
Secure: Security isn't just a goal, but an absolute requirement. Mail delivery is critical for users; it cannot be turned off, so it must be completely secure. (This is why I started writing qmail: I was sick of the security holes in sendmail and other MTAs.)
Reliable: qmail's straight-paper-path philosophy guarantees that a message, once accepted into the system, will never be lost. qmail also supports maildir, a new, super-reliable user mailbox format. Maildirs, unlike mbox files and mh folders, won't be corrupted if the system crashes during delivery. Even better, not only can a user safely read his mail over NFS, but any number of NFS clients can deliver mail to him at the same time.
Efficient: On a Pentium under BSD/OS, qmail can easily sustain 200000 local messages per day---that's separate messages injected and delivered to mailboxes in a real test! Although remote deliveries are inherently limited by the slowness of DNS and SMTP, qmail overlaps 20 simultaneous deliveries by default, so it zooms quickly through mailing lists. (This is why I finished qmail: I had to get a big mailing list set up.)
Simple: qmail is vastly smaller than any other Internet MTA. Some reasons why: (1) Other MTAs have separate forwarding, aliasing, and mailing list mechanisms. qmail has one simple forwarding mechanism that lets users handle their own mailing lists. (2) Other MTAs offer a spectrum of delivery modes, from fast+unsafe to slow+queued. qmail- send is instantly triggered by new items in the queue, so the qmail system has just one delivery mode: fast+queued. (3) Other MTAs include, in effect, a specialized version of inetd that watches the load average. qmail's design inherently limits the machine load, so qmail-smtpd can safely run from your system's inetd.
Replacement for sendmail: qmail supports host and user masquerading, full host hiding, virtual domains, null clients, list-owner rewriting, relay control, double-bounce recording, arbitrary RFC 822 address lists, cross-host mailing list loop detection, per-recipient checkpointing, downed host backoffs, independent message retry schedules, etc. In short, it's up to speed on modern MTA features. qmail also includes a drop-in ``sendmail'' wrapper so that it will be used transparently by your current UAs.
VMailMgr is:
A password checking interface between qmail-popup and qmail-pop3d which replaces the usual checkpassword, as well as an authentication module for Courier IMAP, that provide access to the virtual mailboxes by one of three methods:
IP-based virtual server access (invisible to the POP3 user)
username-based access (username-virtualuser)
hostname-based access (virtualuser@virtual.host or virtualuser:virtual.host)
You should use it if:
You prefer to have the users manage their own domains email accounts, and store their email in their own home dir. (This makes setting up disk space quotas much easier)
Courier-IMAP is:
A server that provides IMAP access to Maildir mailboxes. This IMAP server does NOT handle traditional mailbox files (/var/spool/mail, and derivatives), it was written for the specific purpose of providing IMAP access to Maildirs.
You should use it because:
By default Qmail uses the newer more efficient Maildir format for storing email, and Courier-imap is the only imap server I am aware of that supports Maildir. So in short, if you use Qmail, and want imap support, you have to use it.
The email system you hopefully will get after having read this HOWTO is composed of several parts, the patched Qmail rpms are key to using this document. I recommend using the software versions I tried, they will probably compile without many problems and result in a fairly stable daemon. If you are courageous, you can try to compile all the latest-stuff-with-tons-of-new-features, but don't blame me if something fails ;-). However, you may report other working configurations to be included in future versions of this document. All of the steps were tested on a RedHat Linux 7.2 box, so the HOWTO is somewhat specific, but you should be able to use it for other linux distributions as well.
You do not necessarily have to install in all components. I tried to structure this HOWTO so that you can skip the parts you are not interested in.
The document is neither a user manual to Qmail, VMailMgr nor Courier-imap. Its prime intention is to save email admins some headaches when installing their server and to do my little contribution to the linux community.
Though this document is only able to cover a snapshot in time on a limited number of setups, I am pretty confident that it can help you get your email system up and running. Combinations that work for me are:
RedHat 7.2, Qmail 1.03+patches-18, VMailMgr 0.96.9, Courier-imap 1.4.3
RedHat 6.2, Linux 2.2.14, Qmail 1.03+patches-12, VMailMgr 0.96.6, Courier-imap 0.31
Mandrake 7.0, Linux 2.2.13, Qmail 1.03+patches-12, VMailMgr 0.96.6, Courier-imap 0.31
Debian Potato, Qmail 1.03, VMailMgr 0.96.9, Courier-imap 1.4.3
This document was started on April 18, 2000 by Dan Kuykendall after several installs of Qmail and VMailMgr. Then even more setups when Courier-imap support was ready.
The newest version of this can be found on my homepage http://www.clearrivertech.com/linux/HOWTO as SGML source, as HTML and as TEXT. Other versions may be found in different formats at the LDP homepage http://www.linuxdoc.org/.
Comments on this HOWTO may be directed to the author Dan Kuykendall (dan@kuykendall.org).
v0.1 (April 18, 2000)
Preview version, wasn't in HOWTO format.
v1.0 (April 18, 2000)
Minor corrections.
Added details and put into HOWTO format.
v1.1 (April 19, 2000)
Minor corrections.
Restructured RPM install step.
Added source compile and install steps.
v1.2 (April 19, 2000)
Minor corrections.
Fixed source compile locations and install steps.
Added source compile and install steps.
v1.3 (April 19, 2000)
Minor corrections.
Built proper SGML version (using LinuxDoc DTD).
v1.4 (April 23, 2000)
Updated the Courier-IMAP setup information for new VMailMgr version.
Switched the license to the GNU FDL.
Other minor additions and corrections.
v1.5 (March 11, 2002)
Updated the Courier-IMAP setup information for new VMailMgr version.
Updated links to various websites.
Other minor additions and corrections.
Switched SGML from LinuxDOC to DocBook.
Copyright (c) Dan Kuykendall. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation
A copy of the license is available at GNU Free Documentation License.
Thanks to everyone that gave comments as I was writing this. This includes Bruce Guenter and other members of the vmailmgr-discuss list.