Actually, to be fair, there is a good one and freeware: http://pegasus.quantum.2ya.com/. Combining both servers: Pegassus + Mercury mail you can have more than what you have with Outlook and its server.

If you are lucky enough to find a simple way of learning how to use it plainly, you'll be able to program over it, add filters, PopFile spam filtering, and the limit would be in your imagination. There is a mailing list.

They may integrate with Outlook because you then have to change your email addresses in Outlook as localhost. All the work is handled by Mercury Mail. It classiffies, filters, and fetches the emails.

I have my local Apache 2 sending emails via Mercury Server in a very simple way.

To see/get it integrated with Apache 2 see: http://xampp.sourceforge.net/.