Deliverability
What is Feedback Loop (FBL)?
A program by which a mailbox provider forwards spam complaints back to the sender so they can suppress those recipients.
A feedback loop (FBL) is an arrangement where a mailbox provider sends a report to the originating sender each time one of its users marks a message as spam. Senders enroll their IPs or domains, for example via Yahoo, Microsoft's JMRP, or Validity's Universal FBL, then parse the returned complaint reports, which typically arrive in the ARF format. The standard practice is to immediately and permanently suppress any address that generates a complaint.
Why it matters for cold email
Without an FBL a cold sender is blind to who is complaining and keeps mailing people who will complain again, compounding reputation damage. Enrolling in every available FBL and auto-suppressing complainers is a baseline hygiene step for protecting sending domains.
Related terms
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