At the time the Sendmail program had a very poor reputation with respect to security, with four root vulnerabilities per year for two successive years.

This will surprise some of your readers, but my primary interest is not with computer security. I am primarily interested in writing software that works as intended.

The challenge with Postfix, or with any piece of software, is to update software without introducing problems.

Writing software that's safe even in the presence of bugs makes the challenge even more interesting.

I don't expect an overnight change of all desktops to what the US Military used to call B3 level security. And even that would not stop users from shooting themselves into the foot.

Like all software, Qmail can survive only when it keeps up with changing requirements.

Coming back to the topic of computer security, the TCP Wrapper is an example of such a safety net. I wrote it when my systems were under attack by someone who appeared to walk through walls.