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.
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.