Feedback Loop
Feedback loops notify senders when recipients mark messages as spam, giving teams a chance to suppress those contacts and protect deliverability.
A feedback loop is a complaint signal from a mailbox provider that tells you a recipient marked your email as spam.
Definition and examples
A feedback loop, often shortened to FBL, is a system that passes spam complaints back to the sender or sending platform. When a recipient hits "Report spam," the mailbox provider can send a notice that includes enough information to identify the complaining address or campaign. That lets the sender stop mailing that person and investigate what triggered the complaint.
Not every provider exposes feedback loops in the same way. Some share direct complaint data. Others offer aggregate signals through dashboards or postmaster tools. The practical goal is the same: turn complaints into action before they damage sender reputation and email deliverability.
Why it matters
It matters because complaints are one of the clearest negative signals mailbox providers can see. A few spikes are enough to hurt trust, reduce inbox placement, and make future campaigns harder to deliver.
How teams use feedback loops
The most useful workflow is simple. When a complaint comes in, move that contact to a suppression list immediately, review the message they received, and look for patterns by audience, signup source, or campaign type.
Common mistakes
A common mistake is treating feedback loop data like a reporting metric instead of an operational trigger. If complaints are visible but the contact can still receive the next campaign, the system is not doing its job.
Related terms
Key takeaways
Feedback loops turn spam complaints into usable sender data
The main action is immediate suppression, not passive reporting
Complaint handling protects reputation, inbox placement, and long-term deliverability