The current default mail server for Debian is exim4, though you can use others. As stated already, there are several IMAPs, I've used Courier. Have a look at:Arias, Thanks for your reply and thanks for laying it out in an easy-to-understand manner. I'll try it out!
http://www.trekweb.com/~jasonb/articles/exim4_courier/exim4.html for a description of using both. -- Joe