cyrus-imapd

IMAP (Internet Message Access Protocol) is an Internet standards-track protocol for accessing messages (mail, bboards, news, etc). The Cyrus IMAP server differs from other IMAP server implementations in that it is generally intended to be run on sealed servers, where normal users are not permitted to log in. The mailbox database is stored in parts of the filesystem that are private to the Cyrus IMAP system. All user access to mail is through the IMAP, POP3, or KPOP protocols.