Some users (including me) have noticed that the self-installing QMail package availble from Apple and OS X GNU sometimes hangs at start-up time when the qmail-start command is issued in /var/qmail/rc. To make the situation worse, the hang occurs before any logging takes place, so the poor sysadmin has no idea what went wrong.
This post suggests that the hang may be due to problems with resolving the UNIX user ID of one or more of the qmail-specific UNIX user accounts, and provides a remedy. Cutting right to the chase, the post suggests that the following command (as root):
nidump passwd / > /etc/passwdwill put information about the qmail users (which exists only in the NetInfo database) into the /etc/passwd file, where standard UNIX routines can find them in order to perform username-to-UNIX ID translation.
It worked for me!
[robg adds: I have not confirmed this one...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030708155436720