Mixminion is the standard implementation of the Type III anonymous remailer protocol.

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

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

Eventually, the packet arrives at a final (or "exit") mix, which sends it to the chosen recipient.

Mixminion supports Single-Use Reply Blocks (or SURBs) to allow anonymous recipients.