the phantom remailer

The Phantom Remailer is a pseudonymous single-blind remailer that runs as a delivery agent on a mail server. It was designed for use with Sendmail and other mail transfer agents that support the Sendmail standard. This remailer implements fully SPF and DKIM compatible mail forwarding with a low Spamassassin score.

The remailer works as a transparent forwarder for incoming emails and an anonymizing remailer for outgoing emails. This means you get the full benefit of Multipart/MIME email messages as an incoming address and a stripped down text/plain experience for outgoing messages, even when your reply contains a Multipart message.