greylisting

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greylisting

A spam prevention method in which the receiving mail server rejects a message the first time it is received. The sending server of a legitimate user will eventually retransmit the message. However, the servers that spammers use generally will not because the spammer's goal is to disseminate millions of messages quickly and not have to keep track of which ones fail to reach their destination.

Based on the "Triplet"
When a message is received, the greylisting routine checks the IP and e-mail addresses of the sender and the e-mail address of the receiver (the "triplet"). If the triplet has been accepted before, the message is accepted again. If not, the receiving server sends a "busy" message to the sending server. See blacklist and spam filter.
References in periodicals archive ?
When I did, Facebook suspended my account with no ceremony, and that was followed by the protracted business of security mails, grey listing checks and other interminable processes.
We see that through the use of grey listing in the new aXsGUARD software, the total amount of spam e-mails drop with 40 million spam e-mails per month.
SpamLogic[TM] - anti-spam engine with grey listing & BATV, plus 6 additional filters for further fine-grained control