Have I mentioned that — contrary to the commonly accepted thinking — qmail is the flakiest, least stable MTA out there? Upgrading is a real pain: unless you’re careful, all five qmail users will be re-created with a different UID. And, since the UIDs are different, the newly installed qmail binaries will refuse to work with the (previously installed) qmail queue directories.
Sendmail has its problems, but it is rock solid. There isn’t the same fragility to the installation and it is much more verbose in its error reporting so it is easier to find problems.
I think a big part of the problem is that D.J. Bernstein set out to replace too many components of the standard UNIX system at once. Instead of syslog, he has multilog. Instead of init scripts, he has a supervised services. Instead of using the stock resolver, he prefers djbdns. This much change means you have to learn the “D.J.” way of doing things in addition to the conventional way. You can’t get away from syslog, init scripts and the stock resolver without a substantial amount of work.
Maybe I’m only complaining because I’m in the middle of a big qmail/spamassassin installation. Once it is up and running, it should work fine for months if not years. Its the getting it up and running that is the problem.