Schleuder is a gpg-enabled mailinglist with remailer-capabilities. It is designed to serve as a tool for group communication: subscribers can communicate encrypted (and pseudonymously) among themselves, receive emails from non-subscribers and send emails to non-subscribers via the list.
Schleuder takes care of all de- and encryption, stripping of headers, formatting conversions, etc.
Further schleuder can send out its own public key upon request and receive administrative commands by email.
Read more about the concept.