shaun,
Ah, now that you've listed out your accounts, I think I understand why... I think the mail tab only shows the first four accounts, and since the list is alphabetical, it's probably stopping before it gets to Yahoo.
The nice thing about the Call History tab is that it's really easy to add, at least by comparison to most of the edits.
As for the IT guys, we look at EVERYONE like they're crazy!
It makes sure that people only bug us with real questions, lol. Anyway, just ask one of them what your POP/IMAP/SMTP server address is (probably just mail.domain.com, but better to ask to be safe) and that's really all you need besides the username/password that you already know.