Page "Mixminion" Paragraph 2

Mixminion uses a mix network architecture to provide strong anonymity, and prevent eavesdroppers and other attackers from linking senders and recipients.

Volunteers run servers ( called " mixes ") that receive messages, decrypt them, re-order them, and re-transmit them toward their eventual destination.

Every e-mail passes through several mixes so that no single mix can link message senders with recipients.