Suppression list

A Suppression List is a list of suppressed e-mail addresses used by e-mail senders to comply with the CAN-SPAM Act of 2004. CAN-SPAM requires that senders of commercial emails provide a functioning opt-out mechanism by which email recipients can unsubscribe their email address from future email messages. The unsubscribed email addresses are placed into a "suppression list" which is used to "suppress" future email messages to that email address.

Abuse

A suppression list contains valid email addresses. Suppression list abuse occurs when a third party takes a suppression list and emails messages to the email addresses in the list. The original sender of the email messages who provided the opt-out mechanism may be liable for suppression list abuse.

Protection and tracking

A variety of technological means are used to protect suppression lists and track suppression list abuse. These include neutral third party scrubbing of email lists, distribution of MD5 secure hash suppression lists and distribution of "seeded" email lists.