Feedback Loop (FBL) - Online Help | Zoho Campaigns

Feedback Loop (FBL)

A feedback loop (FBL) is a process for listing spam complaints from your sent email campaigns. Some inbox providers such as Yahoo!, Outlook, and AOL send feedback on spam complaints to the email marketing services responsible for the campaign. 

How FBL works

When a recipient marks an email as spam, this is considered a "complaint". Inbox providers block future emails from that sender from reaching the recipient's inbox. Not all inbox providers send feedback on spam complaints in the form of an FBL. 

As Zoho Campaigns is the sending platform for your messages, we receive the complaints and remove those addresses from your mailing list. The campaign report you receive from Zoho Campaigns includes the complaint rate based on the FBLs from various inbox providers. We suggest you take note of complaints in every campaign report and aim to maintain a complaint rate below0.1%


  1. To maintain good mailing list hygiene.
  1. To help you identify any issue in your mailing practices and tackle complaints.
  1. To track your contacts' behavior.

Some inbox providers who offer FBL

  1. AOL

  2. Zoho Mail

  3. Yahoo!

  4. Outlook

  5. BlueTie

  6. Comcast

  7. Cox

  8. Centrum

  9. Earth Link 

  10. FastMail

  11. La Poste

  12. Mail.Ru

  13. OpenSRS (Tucows)

  14. Locaweb

  15. Synacor

  16. Seznam

  17. Terra Mail

  18. Telenor

  19. XS4All

  20. Italiaonline

  21. United Online

  22. USA.NET

  23. UOL Brazil


Gmail doesn't offer an FBL service but does provide the Postmaster tool to track spam complaints. If you have recipients using Gmail, you can use this tool to examine your email sending practices and identify reasons for delivery failures. 


Only a few inbox providers offer FBL reports. This does not mean there are no complaints from contacts using non-FBL providers. Avoid falling into the common misconception below.

Myth: My campaign report has a complaint rate less than the threshold, so I don't have any spam complaints. 

Reality: You may still have complaints from contacts using non-FBL providers. If your list has only contacts using non-FBL providers, then you will always have a zero complaint rate in the campaign report regardless of how many complaints are made. You can follow our best practices on how to maintain good mailing list hygiene.

FBL from inbox providers can be helpful to analyze your mailing list and sending practice. So, we recommend that you pay attention to our campaign reports and take measures to reduce the complaint rate.
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