In one sense, you can’t use the POP3 server – other than as a transport mechanism.
There are a number of Outlook sharing programs out there – many of them are part of the Microsoft Office application community.
Personally, I use ShareO from 4Team.biz. I identify the folder, calendar, or whatever that I wish to share, and identify the user(s) with whom I wish to share it. Each of us has a copy of ShareO on our systems. Then in the background ShareO sends ordinary emails with numeric coding in the subject line, so that the receiving system knows how to handle it.
Hopefully some other folks can add to this with products they have experience with, but the 4Team website will give you a good general idea of the sorts of things which are possible.