An introduction to qmail
By Gavin Cameron <[email protected]>
This is the first of five articles on qmail that will appear over the next
couple of months. The topics I will cover are
- qmail introduction
- installing and configuring qmail
- virtual domains and qmail
- ezmlm - qmail's mailing list manager
- anti spam and qmail
The qmail WWW page immodestly
touts qmail to be a modern replacement for sendmail but
the purpose of this series of articles is not to bash sendmail,
postfix or any other MTA
(Mail Transport Agent) but rather to document my observations, trials and
tribulations during my implementation of qmail on a number of production
servers.
I'm not going to rehash a heap of qmail documentation from various WWW pages,
instead I'll point you at a number of pages describing qmail, its functionaility
and various add-ons.
A little history
qmail was written by Dan Berstein from University of Illinois at Chicago to
fulfill the following requirements
- Security
- Reliability
- Efficency
- Simplicity
- Replacement for sendmail
Beta testing began in January 1996, gamma testing in August 1996 and version
1.00 was released in February 1997. Since that time a number of small changes
has seen the qmail version number creep up to 1.03. Version 2 is currently
under construction.
The qmail installation package comes with a number of BLURB pages
that my paraphrasing won't do justice to so I'll just list them here for
your viewing pleasure.
That's all well and good if you beleive marketing hype and hopefully my next
couple of articles will sort the chaff from the wheat.
Is qmail secure?
Dan Bernstein offered a $500 reward to the first person to publish a
verifiable security hole in the latest version of qmail: for example, a way
for a user to exploit qmail to take over another account.
The offer still stands. You can find the qmail security
guarantee here.
The structure of qmail
qmail consists of a number of small easily verifiable (securitywise)
programs that perform
well defined tasks. Smaller programs mean that a security flaw in one program
is confined to just that component at the expense of increased overhead
because of additional
fork()s and exec()s required to start the qmail components.
The following links show how all these smaller components fit together
deliver E-mail.
The biggest hurdle
When you install qmail you need to choose whether to use the standard
mbox file format or change to qmail Maildirs. A Maildir is a
lock-free mailbox standard which is reliable over NFS.
The main drawback with moving to Maidirs is MUA support for Maildirs.
Mutt comes standard with Maildir support
and Pine (well its
IMAP server) can be patched to
use maildirs. POP3 support comes standard with qmail and the
Courier-IMAP package gives
you IMAP functionality.
Next time
In my next article I'll be taking you through the installation of qmail,
tcpserver and the daemontools packages that all go together to produce a
highly reliable mail server. Until then, read the URLs listed in this article
in preparation for installing qmail.
URLs from this article
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