A feedback loop (FBL) is a service in which an inbox provider reports back to senders when their recipients press "Report spam". Yahoo, Microsoft and others run them; Gmail offers an aggregated version to large senders.
How senders use it
Email services sign up for feedback loops and automatically stop emailing anyone who complains. That keeps the spam complaint rate down, since a person who complained once will usually do it again.
For cold email
Cold emailers sending from Google Workspace or Microsoft 365 mailboxes don't receive feedback loop reports directly. What you can control:
- A clear way to opt out in every email, and honouring it at once.
- A suppression list so nobody who said no is emailed again from any mailbox.
- The one-click unsubscribe header, which gives people an alternative to the spam button.
mailzy removes anyone who replies asking to be taken off, and slows or pauses a campaign whose opt-outs climb.