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.

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

However, writing software without defects is not sufficient. In my experience, it is at least as difficult to write software that is safe – that is, software that behaves reasonably under adverse conditions.

Defect-free software does not exist.

Sure, but competition is good for the user.

Internally, Postfix does use multi-threading, for example, for its scheduler program that hands the mail queue requests to the mail delivery agents.

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

Like most people, I am not smart enough that I can design software without having to restructure the software every now and then.

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.

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.