perdition

POP3 & IMAP4 proxy that can map users to multiple backend servers

Perdition is a mail retrieval proxy that allows users to connect to a content-free POP3 or IMAP4 server that will redirect them to their real POP3 or IMAP4 server. This enables mail retrieval for a domain to be split across multiple backend servers on a per user basis. It can also be used as a POP3 or IMAP4 proxy in firewall applications. Perdition supports arbitrary library based map access to determine the server for each user - POSIX regex, GDBM, PostgreSQL, MySQL, NIS and OpenLDAP libraries ship with the distribution. The use of perditon to scale mail services beyond a single box is discussed in a paper the author wrote on high capacity email, so be sure to check the web page.