The UW IMAP server is the reference server implementation of the IMAP protocol, developed at the University of Washington. Unlike other server implementations, it is designed to be aggressively compatible with existing legacy mail stores and systems, and to be "plug-and-play" installable without requiring any site-specific configuration.
UW IMAP uses the c-client mail engine that is also used by the Alpine and Pine e-mail clients. c-client supports multiple mail store formats including mbox, MIX, mbx, MMDF, tenex, mtx, mh, mx, and Usenet news spools. c-client also includes support for IMAP, POP3, NNTP, and SMTP Internet protocols.
Also bundled with UW IMAP are POP2 and POP3 servers, the mailutil utility program, and the dmail and tmail mail delivery agents.
UW IMAP is licensed under the Apache License 2.0
Read more about UW IMAP: Future of UW IMAP