I'm sure it doesn't need to be said, but...
Be sure to watch out for what can happen
with out of office or auto-forwarding sorts of things.
I say this because I once had a user
who knew enough to be dangerous. A piece of the business was getting spun
off, and during the transition period they had their old IDs here and new
ones there. This guy set up his old mail to auto-forward to his new one.
Only problem - he had a typo in the new address. It forwarded to an invalid
address, which bounced back with a message that it couldn't deliver, which
it then forwarded to the bad address, which ....
I was a Notes programmer (not an admin
person) involved in the transition, but I got called by our server people
when the endless loop of messages crashed the mail server at our end. My
contribution was figuring out what this guy had done. This was 20+ years
ago so maybe situations like that are caught better now, but it's certainly
stuck in my mind over the years. :-)