What is an email Feedback Loop (FBL)?

A feedback loop (FBL) is a service offered by mailbox providers that reports when recipients mark your emails as spam.

When someone clicks "Report Spam" or "This is Junk," the FBL notifies you, typically by sending a message to an email address you've registered. This lets you remove the complainer from your list and understand what's generating complaints.

Why FBLs matter: Without them, you're flying blind. You'd never know who complained, only that complaint rates are affecting deliverability. FBLs give you actionable data.

Major providers offering FBLs: Yahoo (through their Complaint Feedback Loop), Microsoft (JMRP and SNDS), and various ISPs. Gmail notably does not offer traditional FBL access, relying instead on Postmaster Tools for aggregate complaint data.

How to use FBL data: Immediately suppress complainers from future sends. Analyze complaint patterns: are certain campaigns, subjects, or acquisition sources generating more complaints? Use insights to improve practices.

Setup requires registration. Each provider has their own enrollment process. You need to verify domain ownership and configure where reports are sent. Most ESPs handle this automatically for their shared infrastructure.

Responding to FBL reports is expected. Providers who offer FBLs expect you to act on them. Continuing to email complainers signals poor practices.