Mixmaster Remailers

Some articles on remailers:

Anonymous Remailer - Types of Remailer
... In general, different classes of anonymous remailers differ with regard to the choices their designers/operators have made ... by the legal ramifications of operating specific types of remailers ... Some remailers change both types of address in messages they forward, and the list of forwarding nodes in e-mail messages as well, as the message passes through ...