MasqMail is a mail server designed for hosts that do not have a permanent
internet connection eg. a home network or a single host at home. It has
special support for connections to different ISPs. It replaces sendmail or
other MTAs such as qmail or exim.

Features

    * Delivers only when online to a destination 'outside' your LAN
    * Support for multiple Providers (ie. Mail Servers, or direct delivery)
    * Rewriting of Return addresses (Return-Path:, From:, Reply-To:),
	configurable for each Provider separately
    * can also be used as a Mail Server on a LAN
    * alias support
    * delivery to pipes
    * delivery to MDAs (eg. procmail)
    * Maildir support (version >= 0.2.5)
    * routing depending on sender
    * AUTH (RFC 2554) support (as client, since version 0.1.0)
    * SMTP-after-POP
    * POP3 client
    * POP3 client daemon (fetch mail in regular intervals if online)

WWW: http://innominate.org/kurth/masqmail/