What is the Abuse Reporting Format (ARF)?
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Imagine a recipient hits "Report Spam" on one of your emails. That complaint needs to travel from their mailbox provider back to you (or your ESP) in a way both sides can actually read and act on. That's exactly what the Abuse Reporting Format (ARF) was designed to do.
ARF is a standardized format for packaging email abuse complaints. Before it existed, different providers reported complaints in different ways, which made automated processing a mess. ARF gave everyone a common structure so complaints could flow through feedback loops reliably and without human interpretation each time.
A real ARF report is a multipart MIME message with three parts. The first part is a plain-text summary a human can read. The second is a machine-readable block of metadata (complaint type, reporting address, original recipient, timestamp). The third is a copy of the offending email itself. Your ESP or abuse desk can parse that second section automatically and trigger suppression, investigation, or whatever handling you've set up.
The complaint type field is worth knowing. Common values include "abuse" (spam complaints), "fraud" (phishing or scam reports), and "virus" (malware flags). Most of what senders deal with day-to-day is "abuse" complaints from recipients clicking that spam button in Gmail, Yahoo Mail, or Outlook.
Why should you care? If you're signed up for a feedback loop with a mailbox provider, the complaints come back to you in ARF format. Your ESP typically handles the parsing automatically and adds those addresses to your suppression list. But if you run your own infrastructure or a custom abuse desk, you need to know what ARF looks like so you can actually act on it. Ignoring those complaints is one of the fastest ways to damage your sender reputation.
ARF is defined in RFC 5965. It's not a flashy spec, but it's the backbone of how complaint data moves between organizations at scale.
If you're getting ARF reports and not sure what to do with them, our SOS hotline is free and we're happy to walk you through it.
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