Blacklists

"Blacklists," preferably known by some as "block lists," are usually databases of IP addresses that are known to send spam.  These databases can be utilized by most eMail server software to cross-check the source of all eMail messages in real-time.  If the cross-check yields a positive response (because the sender is blacklisted), the connection can be cut off automatically before message delivery can succeed.

Spammers often view this concept as a form of unfair censorship by the blacklist operators, but in reality the recipients generally agree with the blacklist operator's criteria and have chosen to make use of it to stop spam from getting into their systems.

If you find that an eMail message you sent gets rejected due to blacklisting, you could visit the referenced web page for a more detailed explanation (a link will usually be included), but you'll probably just want to contact your ISP to ask them to get de-listed so that you can send eMail again.  Note that contacting blacklist operators to request a de-listing normally only works for your ISP's staff who operate the eMail system.

More information

• Some well-known blacklists (sorted alphabetically)

See also

• False positive

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