Email anonymity is difficult to achieve because a user provides proof of their identity in the “From field” of a message and the header information contains the email address, the address of the ISP’s outgoing email server and other information. For email to be anonymous this information must be removed from the message header.
A remailer is a service that allows a user to send email without revealing their name, e-mail address, IP address or the ISP used to the receiver or anyone who attempts to monitor the email traffic. There are several flavors of remailers, each with their advantages and disadvantages
- Pseudo Anonymous – This replaces the sender email address with a pseudonym before remailing it to the recipient.
- Cypherpunk – This strips the sender’s email address from the message before remailing it to the recipient. A consequence of this is that the recipient can’t answer the email.
- Mixmaster – This sends messages in fixed sized packets that have been reordered to prevent messages being traced. These remailers require that the user use special software to create the messages.
- Mixminion – Similar to Tor, Mixminion messages are split into packets then sent via separate paths through the mix network. Each packet is encrypted with the public key of each server in its path before it is sent. At each server the packet is decrypted and the message re-ordered before being sent to the next server in the path.
Many remailers operate outside the United States and Europe to avoid the possibility of being forced to divulge customer information to law enforcement agencies.