If you are alright with running a single piece app that provides webmail, SMTP, POP, and REST, you might be interested in my project: http://www.inbucket.org/
It's really targeted for intranet use though, I wouldn't recommend exposing anything other than the SMTP port to the internet.
It's really targeted for intranet use though, I wouldn't recommend exposing anything other than the SMTP port to the internet.