I've just started using Surgemail from http://www.surgemail.com.
Now THIS is the way to go!
I'd tried all the usual sendmail/fetchmail/postfix/pop3/imap stuff and got pretty much nowhere.
Surgemail just leaps into life and works like magic.
It runs my domain, sends and collects mail, and includes a webmail interface for retrieval of mail anywhere on earth.
This software also makes it easy to avoid becoming an open-relay.
And best: the 5-user version is FREE.
I used to run a mail server on Win NT, which was quite easy but quite dicey too. But now I'm finally able to ditch windows for good.
The tech help is the best I've ever seen: I just can't get enough of this product
If you're trying - and failing - to set up your own mailserver, then try this one.
I'm no linux expert, but had very little trouble getting this to sing sweetly.