GNU Anubis is an outgoing mail processor. It goes between the MUA (Mail User Agent) and the MTA (Mail Transport Agent), and can perform on the fly various sorts of processing and conversion on the outgoing mail in accord with the sender's specified rules, based on a highly configurable regular expressions system. It operates as a proxy server, independently from mail user agents. GNU Anubis can edit outgoing mail headers, encrypt and/or sign mail with the GNU Privacy Guard, build secure SMTP tunnels (Simple Mail Transport Protocol) using the TLS/SSL encryption even if your mail user agent doesn't support it, or tunnel a connection through a SOCKS proxy server. --------* --------** ------*** | MUA | ---> | Anubis | ---> | MTA | --------- ---------- --------- * Mail User Agent (client) ** An outgoing mail processor and the SMTP tunnel. *** Mail Transport Agent (server)