| Rev | Author | # | Line |
|---|---|---|---|
| 1 | DanielLawson | 1 | GreyListing is a new technique for reducing the volume of [Spam]. |
| 2 | |||
| 3 | !! About Greylisting | ||
| 4 | |||
| 5 | Greylisting relies on the inherent reliability built into the [SMTP] protocol - basically, you can temporarily reject a message and be reasonably confident that the sending [MTA] will hold on to it and retry later. The idea is that the software spammers use isn't smart enough to deal with temporary rejects - bulk throughput is better than technical correctness in their case. Such software will never reattempt delivery, however real MTAs will. | ||
| 6 | |||
| 7 | Incoming mail is identified by a triplet of data: | ||
| 8 | |||
| 9 | * The IP of the sending host | ||
| 10 | * The envelope sender address | ||
| 11 | * The envelope recipient address | ||
| 12 | |||
| 13 | The first time your MTA receives an email from a specific triplet, it sends a temporary reject notification to the sending MTA. Any real MTA will obey this temporary reject, and resend the email after a delay period. | ||
| 14 | |||
| 15 | There are some other modifications to the above description, such as: | ||
| 16 | |||
| 17 | * If more than one triplet arrives within the first timeout, delay it as well. | ||
| 18 | * If mail for a given triplet hasn't been observed for a significant period of time, remove the records relating to it. | ||
| 19 | |||
| 20 | !! Implementations | ||
| 21 | |||
| 22 | * http://www.maretmanu.org/homepage/inform/exim-spam.html | ||
| 23 | * http://greylisting.org/implementations/ | ||
| 24 | |||
| 25 | !! References | ||
| 26 | * http://www.greylisting.org | ||
| 27 | * [Greylisting Whitepaper|http://greylisting.org/articles/whitepaper.shtml] | ||
| 28 | * http://www.acme.com/mail_filtering/introduction_frameset.html | ||
| 29 | * http://projects.puremagic.com/greylisting/ | ||
| 30 | ----- | ||
| 3 | DanielLawson | 31 | Part of CategoryAntiSpam |
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