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.

Adding functionality is not just a matter of adding code.

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.

Windows favors multi-threading, which means that a service is implemented by one single process.

Qmail out of the box works fine, so people will want to use it regardless of licensing restrictions, even when the software does not ship with their system software.

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.

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