I once again throw myself at the mercy of the bearded linux gods.

I'm setting up a server to handle the web/ftp/audio/mail traffic for the student radio station I help out. I've got the first three sorted without any fuss. I'm now looking at mail, the server will eventually have its own domain with the MX records pointing at it. I want the machine to act as a POP3/IMAP server and also I'll need to provide webmail access too. For sending mail I assume you can just forward all requests onto the universities SMTP server.

It's a Gentoo box BTW

What I'd like to know is.

(a) What software do people recommend? I've read howto's using Cyrus and PostFix to send and Fetchmail and Courier to recieve on Gentoo's forum. But the disclaimer on the site said it difficult to scale/maintain when you've got lots of users (we're looking at probably 100 accounts). Also, a lot of these people won't will never actually login to machine.

(b) Once armed with the information for question a, any good books/HOWTOs to get going?