Keeping most of the software reasonably up-to-date isn't too hard; on Debian, for example, just regularly use apt-get update && apt-get upgrade. (Hopefully you

Keeping most of the software reasonably up-to-date isn't too hard; on Debian, for example, just regularly use apt-get update && apt-get upgrade. (Hopefully you have backups ready in case it goes sideways.) Probably my number one time sink on the mail server is, "Where is the email from X that I've been expecting?" A close number two is, "I'm getting too much spam." If you're paying for hosted email from someone else, you can just give them a call and make it their headache. If you're doing your own, it's your own headache, and it's a headache that can easily consume a few hours at a time. You also should regularly check in with various system and software logs, to make sure that someone isn't trying a novel new attack against the mail server, or that a process isn't struggling for some reason. Most of the software does a pretty good job of being rock-solid, so I don't find myself having to tune things all the time or nudge dead processes or anything. But, I did find that if I left the mail server alone for a while, then when something did go wrong, it took me a lot longer to resolve it (I think mostly because I'd forgotten where everything was), which is not what I want in a downtime situation.