A few major mailbox providers like Gmail, Outlook, and Yahoo notify senders when individual recipients mark their emails as spam or unsubscribe in their mailbox. This service is called the Feedback Loop (FBL) and allows senders to track complaints about their emails. The reports from FBLs list the email addresses that marked emails as spam so the sender can remove them from future mailings.
A Feedback Loop (FBL) is a mechanism that allows email senders to receive feedback from ISPs or mailbox providers regarding recipient complaints and spam reports. It helps senders identify and address issues with their email campaigns, improve deliverability, and maintain a good sender reputation.
FBL reports are recipient-specific – they are not tied to IP addresses or domains. Senders can access them for free when the mailbox provider offers FBL services. Monitoring FBL reports is crucial for senders to estimate how often their emails are marked as spam and stay compliant with inbox providers’ standards. It helps justify complaints and avoid penalization if complaint rates are low.
In addition to FBL reports, every email marketer should maintain a suppression list. This contains email addresses of people who have unsubscribed, bounced or complained about emails. Hard bounces – when an email address no longer exists – are particularly important to add to suppression lists. Soft bounces are temporary inboxes full of errors and don’t need suppression.
Sending to suppressed email addresses damages sender reputation since it indicates disregard for user preferences. Mailbox providers like Gmail will automatically throttle delivery of emails from senders who repeatedly mail suppressed addresses. Eventually, all emails from that sender may be rejected or land in spam folders.
Maintaining a clean and updated suppression list is critical for good sender reputation and inbox placement. It shows respect for subscriber choices and helps build deliverability and engagement over the long run. Monitoring FBL reports and suppression lists together provides visibility into subscriber complaints so marketers can course-correct and avoid damaging blunders.