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.
It allows completly crypted mail transport, remailer capabilities, maintainence via signed mail, etc. It's main propose is to enable political groups to communicate in private via mail.