Feedback loops share complaint signals from mailbox providers back to senders. Learn how FBLs work and how to use them to protect deliverability.
An email feedback loop (FBL) is a mechanism where a mailbox provider sends complaint signals back to a sender when recipients mark messages as spam. It helps senders identify problematic list sources and suppress complainers quickly.
Not all providers offer FBLs the same way, but where available, they’re a strong operational tool for keeping complaint rates low. Complaint suppression is one of the fastest ways to protect reputation.
FBL data should be handled carefully because it can include sensitive identifiers. The best practice is to use it strictly for suppression and investigation, not for marketing or targeting.