When a user of a large mail system such as AOL, Yahoo, or Hotmail reports a message as junk or spam, one of the things the system does is to look at the source of the message and see if the source is one that has a feedback loop (FBL) agreement with the mail system. If so, it sends a copy of the message back to the source, so they can take appropriate action, for some version of appropriate. For several years, ARF, Abuse Reporting Format, has been the de-facto standard form that large mail systems use to exchange FBL reports about user mail complaints.

Until now, the only documentation for ARF was a draft spec originally written Yakov Shafranovich (CircleID) in 2005, and occasionally updated originally by him and later by other people including myself. Earlier this year, the IETF chartered a working group called MARF which took that draft, brought the references up to date, stripped out a lot of options that seemed useful five years ago but in practice nobody ever used, and this week it was finally published as RFC 5965.

ARF (or now MARF) is quite simple, a version of the existing Multipart/Report message format that includes information about the report, such as the address of the recipient, descriptive text for a human reader, and a copy of the offending message. Having a standard format for reports, simple though it is, makes them much easier to process. For my tiny system, for example, nearly all of the trickle of reports are about mailing list messages. When a FBL report arrives, an automated script looks at the report and the message, and in the usual case that it’s from a mailing list, it creates an unsubscribe request to remove the person from the list. Otherwise, it passes the message along to the human manager so I can decide what, if anything, to do about it. Larger mail systems also use them to collect statistics about their mail-sending customers.

The IETF process works particularly well when it standardizes existing practice, and ARF/MARF is an excellent example of that. The differences between the earlier drafts and the final version make it clearer and more precise, and it’s now a proper standard we can cite:

Abuse Reporting Format! Ask for it by name: RFC 5965!