Life with qmail

Author : Dave Sill
Publication Date : 2 January 2006

Book Summary:

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.

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.

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

Why use qmail:

Your operating system included an MTA, probably Sendmail, so if you're reading this document you're probably looking for something better. Some of the advantages of qmail over vendor-provided MTA's include:

- 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.

- Performance

qmail parallelizes mail delivery, performing up to 20 deliveries simultaneously, by default.

- 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.

- Simplicity

qmail is smaller than any other equivalently-featured MTA.

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