A suppression list is a list of suppressed

e-mail addresses An email address identifies an email box to which messages are delivered. While early messaging systems used a variety of formats for addressing, today, email addresses follow a set of specific rules originally standardized by the Internet Engineer ...

used by

e-mail Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...

senders to comply with the

CAN-SPAM Act The Controlling the Assault of Non-Solicited Pornography And Marketing (CAN-SPAM) Act of 2003 is a law passed in 2003 establishing the United States' first national standards for the sending of commercial e-mail. The law requires the Federal Tra ...

of 2003 (United States of America). 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. Additionally: Suppression files are to be used when you are emailing a particular campaign. Email addresses in suppression lists are NOT to be included while emailing; those people have chosen not to receive emails for that product. Alternately, in terms of

email marketing Email marketing is the act of sending a commercial message, typically to a group of people, using email. In its broadest sense, every email sent to a potential or current customer could be considered email marketing. It involves using email to ...

, Suppression lists contain email ID's that have already chosen to OPT-OUT from getting email updates of that particular product.

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

hash Hash, hashes, hash mark, or hashing may refer to: Substances * Hash (food), a coarse mixture of ingredients * Hash, a nickname for hashish, a cannabis product Hash mark *Hash mark (sports), a marking on hockey rinks and gridiron football field ...

suppression lists and distribution of "seeded" email lists. The best practice in distributing these lists is to avoid sending the email addresses themselves as plaintext, but instead send a list with one "hash" per line, each hash generated from an email address using a one-way

cryptographic hash function A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography: * the probability of a particular n-bit output ...

. Internal mailing lists can be scrubbed by using the same hash function to generate one "hash" for each email address on internal mailing lists, and if the internally generated hash matches any of the hashes on the suppression list, then the corresponding email address on the internal mailing list *should* be removed. Because the hash is one-way, it's not possible for a person to recover the original email address if that person only has the code, making it impossible for that email address to accidentally or deliberately be *added* (rather than removed) from internal mailing lists.

References

{{reflist Email