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A feedback loop (FBL) is a service provided by email providers that notifies senders when recipients mark their emails as spam. When a subscriber clicks the spam button in their inbox, the email provider sends a report back to the sender, allowing them to remove that person from their mailing list and investigate why the complaint occurred.
Feedback loops are essential for maintaining good sender reputation and email deliverability. Spam complaints are one of the most damaging signals to your reputation - even a small number can significantly impact inbox placement. By processing FBL reports, you can immediately stop sending to people who complained, preventing further damage. Feedback loops also provide valuable insights into which campaigns, content, or sending patterns generate complaints. A complaint rate above 0.1% is a warning sign, and rates above 0.3% can trigger spam filtering or account suspension.
When a recipient marks your email as spam, the email provider generates a complaint report in ARF (Abuse Reporting Format) format. This report is sent to the email address you registered with the feedback loop program. The report contains information about the complained message, including headers that help identify which campaign and subscriber generated the complaint. Your email system should automatically process these reports to suppress the complaining address from future mailings. Major providers like Yahoo, Microsoft (Outlook/Hotmail), and AOL offer feedback loop programs. Gmail does not offer a traditional FBL but provides complaint data through Google Postmaster Tools.
Each email provider has its own signup process. For Microsoft, register at Microsoft SNDS and JMRP. For Yahoo, use the Yahoo Complaint Feedback Loop. AOL uses the same system as Yahoo (Verizon Media). Gmail does not offer a traditional FBL - instead, use Google Postmaster Tools to monitor complaint rates. Most ESPs handle FBL registration and processing automatically.
Keep your spam complaint rate below 0.1% (1 complaint per 1,000 emails). Rates between 0.1% and 0.3% are concerning and require investigation. Rates above 0.3% will likely trigger spam filtering and may result in account suspension with your ESP. Google specifically requires bulk senders to stay under 0.3%.
People mark emails as spam when: they do not recognize the sender, the unsubscribe link is hard to find, they signed up accidentally or forgot they subscribed, the content is not relevant to them, or they receive too many emails. Make unsubscribe easy and prominent, set clear expectations at signup, and send relevant content to reduce complaints.
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