QMail: A Better Sendmail?

This modular suite of e-mail programs offers scalability, security, and simplicity of administration. Better yet, it's more efficient than Sendmail. Best of all, it's free!

by Lisa Phifer VP Core Competence, Inc. [March 2, 2000]

Last summer, during a visit to our local ISP, NetReach, Director of Technical Operations George Carey told me that he was trialing a very promising Sendmail alternative: an open source message transfer agent called QMail. Created by D.J. Bernstein, QMail is designed as a wholesale replacement for Sendmail on any UNIX platform, including AIX, BSD, FreeBSD, HP-UX, Irix, Linux, OSF/1, SunOS, and Solaris. What makes QMail so promising? According to Carey, Bernstein "built QMail from the ground up, taking a sys admin approach. Admins want more flexibility, performance, and security. QMail gives you all of that."

Carey was looking for volunteers to try QMail. I needed little convincing: Our company domain was relocated to NetReach's QMail server the next day.

Six months later, I sat down with Carey to discuss his experiences, recommendations, and thoughts about replacing Sendmail with QMail.

What is QMail?
QMail is a simple, compact, modular suite of mail programs. Its major components include:

There are also many other utilities and related packages for use with QMail, including:

As should now be apparent, QMail is highly modular: It is this modularity that makes it so flexible, lightweight, and secure.

How does modularity make QMail secure?
As described by Carey, "QMail isn't one big, monolithic Sendmail. One QMail program listens to the smtp port, another spools incoming mail, and still another feeds messages to users. Each program runs with the permissions it needs and nothing more."

Only qmail-start runs as root so that it can bind to the smtp port; only qmail-queue sets uid for user mailbox access. QMail enforces clear separation between addresses, files, and programs. Bernstein is so confident in the security of this approach that he's offered a reward for anyone who can find a loophole.

According to Bernstein, "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."

Beyond the security inherent in QMail's architecture, application-level security features include anti-relay protection to block spam and a checkpassword plug-in that allows integration of proxy authentication. For example, you can consult an LDAP server when users log into their mailbox using SqWebMail.

goto Page 2: Efficiency: the Big Draw