ARF (Abuse Reporting Format)
ARF (Abuse Reporting Format), defined in RFC 5965, is a machine-readable email format mailbox providers use to report a specific message back to whoever sent it -- most often a spam complaint, but also an authentication failure or virus report -- as a structured multipart/report instead of free text a human has to interpret. It's the format behind classic ISP feedback-loop (FBL) programs, where a mailbox provider forwards a copy of every message a user marks as spam back to the sending server's registered abuse address, letting a legitimate sender catch and remove complaining recipients before enough complaints accumulate to damage its reputation. DMARC's optional ruf (forensic) reports also use ARF as their base format, extended by RFC 6591 and RFC 6652 to carry DKIM- and SPF-specific failure detail, though most large mailbox providers send only DMARC's aggregate rua reports, citing the privacy cost of sharing message-level detail. Unlike a DNSBL listing, which reflects an IP's aggregate reputation, an ARF report identifies one specific message, when a receiver sends one at all.
By AdminKit team, Netbase JSC · Updated