Feedback Loop (FBL)
A feedback loop is a service from a mailbox provider that notifies a sender when a recipient marks their email as spam, so the sender can suppress that address.
A feedback loop, or FBL, is a service offered by some mailbox providers that notifies a sender whenever one of their recipients marks a message as spam. Instead of the complaint staying invisible, the provider passes it back to the sender, who can then remove that recipient from all future sends. It turns a hidden negative signal into actionable information.
Why it matters for outbound
Feedback loops are a key tool for protecting sender reputation. A recipient who reports spam is telling you clearly that they do not want your mail, and continuing to contact them only invites more complaints and deeper reputation damage. Honoring FBL signals immediately keeps the spam complaint rate low and demonstrates to providers that you are a responsible sender. For outbound at scale, acting on every complaint is the difference between a self-correcting program and one that spirals.
Outword treats every complaint signal as a hard stop, suppressing the recipient at once to protect deliverability.
How it works
- A recipient clicks "report spam" in a participating provider.
- The provider sends a complaint report back to the sender through the feedback loop.
- The sender adds the address to a suppression list and never contacts it again.
Not every provider runs a public FBL, so complaint management also relies on broader list hygiene and sharp targeting to keep complaints rare in the first place.
From definitions to pipeline
Outword turns outbound theory into a running motion. Book a call to see what that looks like for your team.