This server provides POP3 access to Maildir format mailboxes. It does not handle traditional mailbox files. It is part of the Courier mail server (http://www.courier-mta.org) but can be configured as a standalone POP3 server. Features include an extremely small memory footprint, abstract authentication modules (e.g. /etc/passwd, LDAP, PAM), virtual mailbox support, resource controls, SSL/TLS, and IPv6 support.
WWW: http://www.courier-mta.org/imap/