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

Defect-free software does not exist.

Most of the effort in the software business goes into the maintenance of code that already exists.

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.

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.

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.

I want to avoid locking people into solutions that work only with Postfix. People should have a choice in what software they want to use with Postfix, be it anti-virus or otherwise.