This is a tale about getting rid of postfix-watch.If you using mac os x server, and started up postfix by using postfix start, you may have noticed that postfix gets shut down by postfix-watch. postfix-watch is a daemon that starts up postfix when needed, and shuts it down when it is inactive. However, this is bad if you want postfix to listen for connections. You could use server admin to change the config, but if you made any changes to your main.cfg file, server admin may stomp on the file.
The easiest thing to do it do it yourself (“if you want something done right, darn it, do it yourself!”). It is simple. postfix-watch is started up by the startup item Postfix (in /System/Library/Startup Items/Postfix). If it sees "MAILSERVER=-AUTOMATIC-" or "MAILSERVER=-NO-" in /etc/hostconfig, the startup item starts up postfix-watch. If the startup item sees "MAILSERVER=-YES-", then it starts up postfix and leaves it running. To do it manually, edit /etc/hostconfig, change "MAILSERVER=-NO-" to "MAILSERVER=-YES-", kill postfix-watch, and start up postfix with postfix start.