Gmail Feedback Loop

What is an email feedback loop and how does it work?

An email feedback loop, also known as a complaint feedback loop, enables an Inbox service provider (ISP) to inform a sending organization about spam complaints submitted by recipients of their messages. Doing so, allows the sender to remove those email subscribers from their lists and ensures they won’t continue receiving unwanted messages and file more spam complaints, thus harming their sender reputation.

Each ISP offers its own feedback loop (FBL), and it’s mandatory for a sending organization, whether that’s an email service provider (ESP) like Sendgrid or a business handling email on its own, to register for each one. A typical FBL uses a button or a link to a form that allows a recipient to register a complaint about unwanted email.

Some ISPs send the details of each individual spam complaint to the sending organization while others, such as Gmail, provide aggregate data that doesn’t say which recipients filed complaints (Google Postmaster Tools). The sender that generated the email should immediately remove people who file spam complaints from their mailing list, preferably through an automated process that eliminates the potential for human error. 

What is Gmail’s FBL and can we implement this?

It's a known fact that Google is a provider who does not share a traditional Feedback loop, as explained above, however they have released the option for mass senders to configure Gmail’s FBL.

Having in mind the non-traditional Feedback loop, at the moment we cannot reflect Spam complaints of Google recipients in our Leanplum dashboard. We’ve researched the option of implementing Gmail’s FBL but unfortunately there isn't a way to do so at the moment.

The reason behind this is that an additional header is required. To allow us to insert such a header, our ESP expects change in the API version we use at the moment. We’re currently investigating a possible API migration, however we can’t say for sure when or if it will happen at all.


Even though Gmail’s FBL is not an option, you can still refer to Google Postmaster's "Spam Rate" section of Google Postmaster’s tools:​


The spam report rate indicates the aggregate amount of complaints for Google only - other Spam complaints are reported back to Leanplum. Still, the amount of spam reports doesn't show you what percentage of your emails go to the recipient's Inboxes, and how many are delivered as Spam. This ratio can only be measured via seed testing (services like Validity, Email on Acid, Litmus, etc). You can find more information in our article linked here: Email Seed testing.

Should you have any additional questions on the matter, feel free to reach out to us by emailing 

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