Home Feedback Loop Resources

Please Note: M3AAWG is presenting the educational information listed here as a service to the industry as we recognize that complaint feedback loops are a valuable tool for reducing spam and protecting end-users. However, M3AAWG does not endorse or recommend any particular provider or resource. While our website includes links to materials created by various third parties, their products are not affiliated with the Messaging, Malware and Mobile Anti-Abuse Working Group and M3AAWG has no control over third-party content we reference from time to time. The links and information are provided here “as is” without any responsibility for the material and solely for the user’s convenience.

What is a Complaint Feedback Loop?

The traditional definition of a complaint feedback loop (FBL) is a mechanism by which a Mailbox Provider (MBP) reports user complaints -based on when a user clicks the “Spam” or “Junk” button, back to the verified sender of the email message. MBPs provide this service to senders to help the sender keep their database clean of subscribers who no longer want to receive the sender’s mail and to improve the relevancy of their mail programs. Not all MBPs provide this service and there are conditions to enroll as a sender. The diagram below provides a general overview of how these work.

How Feedback Loops Work

M3AAWG is providing a list of some currently available complaint feedback loops here as an industry service. Feedback loops today are presented in a variety of formats that cue off of different email header components.  In some cases, they also provide the sender with other information, in addition to user complaints.


Complaint Feedback Loop Formats

Traditional (IP-based)

This format, outlined in RFC 6449, is the standard used by MBPs to report user complaints back to the sender. It is based on the sending IP and reports are sent in the industry standard Abuse Reporting Format (ARF), which provides the sender with the full message and identification of the user who complained. This format allows the sender to identify and remove subscribers who register complaints from their database. 


An Aggregate FBL format is an alternative to the Traditional IP-based format and rolls up aggregate counts of complaints by IP, domain, or an identifier determined by the sender.

Providers of an Aggregate FBL format are more sensitive to sharing the Personally Identifiable Information (PII) of their users.  Therefore, this format does not provide the sender with the full message and does not identify the user who complained about the email.  Although user-specific data is not provided, the aggregate statistics provide the sender with valuable information about how their email program is performing.


Like the Traditional FBL format, Domain-based FBL reports are sent in the industry standard Abuse Reporting Format (ARF), which provides the sender with the full message and information on the user who complained about the email received.  What is different is that the Domain-Based FBL format is based on the sending domain. Senders must sign their mail with DKIM (DomainKeys Identified Mail) to participate in the program and enter the sending domain (d= value in DKIM signature) and the selector (the s= value in DKIM signature) from the DKIM signature during the sign-up process.  This format allows senders on shared IP addresses to receive feedback about their specific email program. 


Currently Available Complaint Feedback Loops: 

Traditional (IP-based):


Bluetie/Excite:  https://fbl.validity.com/ 

Comcast:  https://fbl.validity.com/ 

Cox:  https://fbl.validity.com/ 

Earthlink: fblrequest@abuse.earthlink.net    

Fastmail:  https://fbl.validity.com/  

Gandi: https://fbl.validity.com/  

Italiaonline (Libero and Virgilllo): https://fbl.validity.com/ 

La Poste: https://fbl.validity.com/ 

Locaweb: https://fbl.validity.com/ 

Mail.Ru: https://fbl.validity.com/ 

Microsoft JMRP:  https://postmaster.live.com/snds/JMRP.aspx?wa=wsignin1.0 

OpenSRS/Tucows:  https://fbl.validity.com/ 

QQ.com:  http://open.mail.qq.com/ (In Chinese)

Rackspace (formerly Mailtrust):  https://fbl.validity.com/ 

Seznam: https://fbl.validity.com/

SFR: https://fbl.validity.com/ 

SilverSky (formerly USA.NET): https://fbl.validity.com/ 

Swisscom: https://fbl.validity.com/

Synacor:  https://fbl.validity.com/ 

Telcom Italia: https://fbl.validity.com/ 

Telenet: https://fbl.validity.com/ 

Telenor: https://fbl.validity.com/ 

Terra:  https://fbl.validity.com/ 

United Online/Juno/Netzero: http://www.unitedonline.net/postmaster/whitelisted.html 

UOL: https://fbl.validity.com/ 

Virgin Media: https://fbl.validity.com/ 

Ziggo: https://fbl.validity.com/


Aggregated FBLs:


Gmail:  https://support.google.com/mail/answer/6254652?hl=en 

Microsoft SNDS:  https://sendersupport.olc.protection.outlook.com/snds/index.aspx 

Signal Spamhttps://www.signal-spam.fr/  (Requires paid Signal Spam membership)




Comcast:  https://fbl.validity.com/ 

Gandi: https://fbl.validity.com/ 

La Poste: https://fbl.validity.com/ 

SFR: https://fbl.validity.com/ 

Yahoo!: https://senders.yahooinc.com/contact#complaint-feedback-loop 


Additional Resources

Validity's Universal Feedback Loop (https://fbl.validity.com/) powers most of the feedback loops referenced above. 

M3AAWG Feedback Reporting Recommendation, February 2014:



RFC 6449 - Complaint Feedback Loop Operational Recommendations



If you would like us to consider adding a complaint feedback loop to this list, please use our website Contact Us form to send us a short description of the service and the FBL signup URL