Like most people, I am not smart enough that I can design software without having to restructure the software every now and then.
The Postfix security model is based on keeping software simple and stupid.
My reply is: the software has no known bugs, therefore it has not been updated.
Like all software, Qmail can survive only when it keeps up with changing requirements.
Most of the effort in the software business goes into the maintenance of code that already exists.
Defect-free software does not exist.