Qpopper is the most widely-used server for the POP3 protocol. Qpopper
supports the latest standards, and includes a large number of optional
features. The Qpopper homepage is:

  o <http://qpopper.sourceforge.net/>

Do *not* install popper 1.831beta (or any version of Berkeley POP). It is
vulnerable to buffer overflow attacks. Use qpopper instead.

A second alternative is the free IMAP developer's kit from The University
of Washington, Computing & Communications department.  The kit includes
sources for an imapd server, an `ms' demo client, pop2 and pop3 servers,
and a C-client library.  Download from:

  o <ftp://ftp.cac.washington.edu/mail/>

If you are running Qmail, Exim, or Postfix as your mail server and you
have maildirs configured, the best way to go is Courier IMAP, available
at:

  o <http://www.courier-mta.org/imap/>