Glossary
Feedback Loop (FBL)
A feedback loop is a service where mailbox providers forward spam complaints (FBL reports) to the sender when users click “Report spam.” Registered senders receive complaint notifications so they can remove complainers and fix content. FBLs reduce future reputation damage.
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Major providers run FBL programs — usually via Postmaster tools or ESP integration. Not all mail generates FBL events.
FAQ
Is FBL the same as DMARC rua?
No — rua is aggregate auth; FBL is complaint forwarding.
What should I do with an FBL complaint?
Remove the subscriber and review content/frequency.
Do all ISPs offer FBL?
No — large ones often do; coverage varies by region.