Adding functionality is not just a matter of adding code.

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.

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.

Postfix keeps running even if one Postfix process dies; Windows requires that someone restarts the service.

As of today, the Postfix mail transport agent has almost 50,000 lines of code, comments not included.

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.