Sources to be filtered, and the mail will not be accepted.Įarly references for greylisting descriptions and implementations can Source, then by the time it retries, it will appear in a list of Mail from newly seen IP addresses on the theory that, if it's a spam Another application of greylisting is to delay Mail from unfamiliar sources with a "transient (soft) fail" (4xx) The next address in its list since, in spamming, volume counts forįar more than reliability. That is, if the spamware cannot deliver a message, it just goes on to Retransmission attempts after receiving an SMTP temporary failure.
In particular, such software does not perform The purpose of thisįor many years, large amounts of spam have been sent through purpose-īuilt software, or "spamware", that supports only a constrained With an SMTP temporary failure for any reason. There is some confusion in the industry that conflates greylisting It also defines terminology to enable clearĭistinction and discussion of these techniques. This memo documents common greylisting techniques and discusses theirīenefits and costs. Greylisting is useful for removing a large amount of The firehose of spam over the Internet represents a wide range of Some spamware does indeed route around this Terms of its application in the SMTP sequence) and surprisingly Greylisting happens to be a technique that is cheap and early (in They range in cost, effectiveness, and types of Implementations of this basic concept and predictably, therefore,Ībsent a perfect abuse-detection mechanism that incurs no cost, theĬurrent requirement is for an array of techniques to be used by eachįiltering system.
Narrow use of the term refers to generation of an SMTP temporaryįailure reply code for traffic from such sources. (typically measured in minutes or a small number of hours). Of service for an unknown or suspect source, over a period of time Broadly, the term refers to any degradation Reputation this can justify providing degraded service, until there In some cases, an actor does not have a known Good actors and bad actors, giving each significantly different Preferred techniques for handling email abuse explicitly identify The Trust Legal Provisions and are provided without warranty as Include Simplified BSD License text as described in Section 4.e of Code Components extracted from this document must Please review these documentsĬarefully, as they describe your rights and restrictions with respect This document is subject to BCP 78 and the IETF Trust's Legal
Information about the current status of this document, any errata,Īnd how to provide feedback on it may be obtained atĬopyright (c) 2012 IETF Trust and the persons identified as the Internet Standards is available in Section 2 of RFC 5741. Internet Engineering Steering Group (IESG).
Received public review and has been approved for publication by the It represents the consensus of the IETF community. This document is a product of the Internet Engineering Task Force This is an Internet Standards Track document. Repertoire of current anti-abuse email filtering systems. Greylisting is an established mechanism deemed essential to the Providing temporarily degraded service to unknown email clients as an This document describes the art of email greylisting, the practice of ISSN: 2070-1721 Brandenburg InternetWorkingĮmail Greylisting: An Applicability Statement for SMTP Internet Engineering Task Force (IETF) M.