feedback loop email

What is an FBL (Feedback Loop) email?

In the world of email, Feedback Loops enable Mailbox Service Providers (MSPs) to inform Email Service Providers (ESPs) of spam complaints related to their mailings.

How does Feedback Loop work?

fbl schema.excalidraw min

The ESP sends an e-mail to the mailbox provider, who delivers it to the user.

The user indicates that it is spam. The Mailbox Service Provider provides the information to its spam filter so that it can take this information into account for future mailings.

If the MSP provides its own FBL mechanism, it transmits a report in ARF format (explained below). If not, it may partner with a third party to transmit the ARF report.

3 Types of Feedback Loop :

Traditional FBL (IP-based) – RFC 6449

This type of feedback loop (FBL) is the standard used by messaging service providers (MSPs) to report user complaints to senders. Based on the sender’s IP address, reports are transmitted in Abuse Reporting Format (ARF). This format provides the sender with the complete message and identification of the user who filed the complaint.

The sender can identify and remove from his database subscribers who have lodged complaints.

Agregated FBL

The aggregated FBL format is an alternative to the traditional IP-based format and groups complaints aggregated by IP address, domain or an identifier determined by the sender.

This type of FBL does not identify the user who has complained about receiving spam, so the sender cannot unsubscribe the complainant from his or her mailing list, but it does make it possible to track the performance of these e-mailings.

Domain-based FBL

Like traditional FBLs, domain-based FBLs are sent in ARF (Abuse Reporting Format), providing the sender with the complete message and information on the user who filed the complaint. The main difference is that this type of FBL is based on the sender’s domain. To participate in this program, senders must sign their e-mails with DKIM (DomainKeys Identified Mail) and provide the sending domain (value d= in the DKIM signature) as well as the selector (value s= in the DKIM signature) during registration.

The sender can identify and remove subscribers with complaints from his database.

Which mailbox provider offers Feedback Loop?

If you follow this blog, you’ll have seen our article announcing the release of the new Yahoo Sender Hub, which features Complaint Feedback Loop management.

Here’s a list of MSP FBLs by type, with a link to subscribe.

TypeMailbox Service ProviderFeedback Loop ProviderAccès
IPMicrosoft JMRPAuto-gérée
IP / DomaineComcastValidity
IPLiberty GlobalValidity
Agrégée / IPSFRSignal Spam
Validity (Réservée aux membres Signal Spam)
IPUOL MailValidity
IPVirgin MediaValidity
IP / DomaineGandi.netSignal Spam
Validity (Réservée aux membres Signal Spam)
IP / DomaineLaposte.netSignal Spam
Validity (Réservée aux membres Signal Spam)
Agrégée / IPOrangeSignal Spam (Réservée aux membres Signal Spam)
IPUnited Online/Juno/Netzero

Validity (Ex Return-Path for those who know it) proposes an FBL they call Universal

This FBL, which was free of charge, enabled MSPs to offer an FBL easily, but Validity decided to make it chargeable, which in fact has an impact because the price is very high, and many ESPs are wondering about this new charge.

What is XARF Report format?

I told you about ARF (Abuse Report Format), and now there’s XARF, which stands for eXtended Abuse Reporting Format.

Mindbaz has written an article on XARF if you’d like to know more!

It’s a format to keep an eye on

Spam complaints in Sweego

With Sweego, you can track the performance of your campaigns, especially your spam complaints.

Spam Complaints Sweego


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