"I worked at a hosting company a few years ago that still used qmail (and Apache 1.3, and this was in 2010); there was a slight misbehaviour in qmail which we needed to change, which resulted in one of our sysadmins (who didn't really know C) spending days reading, changing, compiling, testing, and debugging code which, with Postfix, would have been a one-line config change. And who knows if it's robust? He stopped working on it once he had a solution that passed his test without segfaulting immediately."
Anecdotal, please provide a link to the qmail mailing list with evidence.
Anecdotal, please provide a link to the qmail mailing list with evidence.