FEmail Deliverability Glossary

Feedback Loop (FBL)

A service offered by major ISPs that notifies senders when recipients mark their email as spam, enabling immediate list suppression.

A feedback loop is a service offered by major ISPs that notifies senders when one of their recipients marks an email as spam. When a recipient clicks "Report Spam," the ISP sends a copy of the complaint to the sender.

Major FBL providers:

Gmail: Uses aggregate data via Google Postmaster Tools rather than individual FBL notifications
Outlook/Hotmail: Microsoft's JMRP (Junk Mail Reporting Program)
Yahoo: Yahoo FBL program
AOL: AOL FBL

Why FBLs matter:

They allow senders to identify and immediately remove complaining recipients
They provide early warning before complaint rates reach dangerous levels
They help identify which campaigns, segments, or types of content generate complaints

What to do with FBL data: Immediately add anyone who files a complaint to your suppression list. Analyze complaint patterns to identify problematic segments or sending behavior.

Frequently Asked Questions

How do I register for ISP feedback loops?

Each major ISP has its own registration process. Microsoft JMRP: register at postmaster.live.com/snds/JMRP.aspx — you'll need to verify your sending IPs. Yahoo FBL: register at postmaster.yahooinc.com/contact/feedback-loops. AOL FBL: register at postmaster.aol.com. Gmail doesn't offer individual complaint notifications — instead, access your spam rate data through Google Postmaster Tools after verifying your domain. For all FBL registrations, provide the email address where complaint notifications should be delivered and ensure your suppression system automatically processes those complaints.

What should I do when I receive an FBL complaint notification?

Act on it within 24 hours. The complaint notification includes the email address of the person who complained — add it to your permanent suppression list immediately. Never re-send to a complaint filer under any circumstances. Then investigate the pattern: was this complaint from a recent campaign? A specific segment? A particular subject line? One complaint per thousand sends is within normal range. Three complaints in a single day from the same campaign or audience segment signals an urgent list quality or targeting problem that needs investigation.

Does Gmail send feedback loop notifications?

Gmail does not send individual complaint notifications in the traditional FBL sense. Instead, Google aggregates complaint data and makes it available in Google Postmaster Tools as a daily spam rate percentage. You can see trends and overall levels but not individual complaint details. This means you can't suppress individual Gmail complainers based on FBL data — you need to manage Gmail deliverability through list hygiene and engagement practices. The Gmail spam rate in Postmaster Tools should be your primary monitoring metric for complaint-driven deliverability issues.

Related Terms

Complaint Rate (Spam Complaint Rate)

The percentage of recipients who click 'Mark as Spam.' Google's 2024 guidelines treat anything above 0.10% as a serious deliverability risk.

Suppression List

A do-not-contact database of unsubscribers, complainers, and hard bounces. Sending to suppressed addresses during warm-up immediately damages reputation.

Gmail Postmaster Tools

Google's free service that shows domain reputation, spam rate, authentication pass rates, and delivery errors for mail sent to Gmail. The most important warm-up monitoring tool.

Microsoft SNDS (Smart Network Data Services)

Microsoft's free service showing sending data and filter verdicts for Outlook.com and Hotmail delivery — the Microsoft equivalent of Google Postmaster Tools.

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