Deliverability
Feedback loop (FBL)
A service where ISPs notify senders when recipients mark their emails as spam.
Definition
A Feedback Loop (FBL) is a service provided by mailbox providers that notifies senders when recipients mark their emails as spam. When a complaint is filed, the FBL sends a report to the sender containing the original email (with the complaining address often redacted). This allows senders to remove complainers from their lists and identify content or targeting issues.
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