Glossary Home

Feedback loop

What is a feedback loop?

A feedback loop (FBL) in emails is a system that sends a notification from the recipient’s internet service providers (ISP) to the email sender if the email is marked as spam or junk. This system is crucial in email deliverability management because it enables senders to receive notifications when there’s an issue with the email. It helps senders understand how their messages are received and provides them the opportunity to take corrective actions. Depending on the provider, the reports can be granular (listing specific recipients who complained) or aggregate data at the campaign or product level.

How does a feedback loop work?

Here’s a step-by-step look at how a feedback loop process works:

1. Email is sent  
   The sender delivers an email to the recipient. Each message includes unique identifiers that help the receiving ISPs track the source, like the sender’s IP address, domain, and headers.

2. Recipient performs an action
    If a recipient considers the message to be unsolicited, they click on the "Report spam" or "Move to junk" action on their email client.

3. Complaint is recorded by the ISP
    The recipient’s ISP or mailbox provider records this action as a spam complaint event tied to the specific sender source.

4. Feedback is sent
   If the sender is enrolled in that the ISP’s feedback loop program, the provider generates an ARF (Abuse Reporting Format) message—a standardized complaint report that contains metadata about the message (headers, sending IP, complaint time, and reason).

5. Sender receives a notification
   The sender’s email system receives the feedback report and identifies the complaining recipient’s address.

6. Sender takes corrective action
   The sender then takes corrective actions to avoid sending future emails to the complaining email address. For example, the address can be added to suppression lists. Complaint data is used to identify trends, problematic email sending or content issues.  

Feedback loop report format

Most feedback loops use the standard Abuse Reporting Format (ARF). An ARF report generally includes:

• Email headers (to identify the original message)

• Reporting MTA or ISP information

• Complaint type (abuse, fraud, phishing)

• Original message sample

• Timestamp and unique identifiers

Senders or ESPs parse these reports automatically to process complaints efficiently.

Why do feedback loops matter?

Feedback loops are important in maintaining a good sender reputation. They benefit both senders and recipients by ensuring transparency, feedback, and accountability.

For senders  

• Protects sender reputation: Timely feedback helps reduce recurring spam complaints that negatively affect sender reputation.

• Improves deliverability: Sending sources with lower complaints and good engagement deliver better emails. Monitoring complaints through feedback helps keep complaints low.

• Boosts audience quality: FBLs helps filter out uninterested or disengaged recipients.

• Meets compliance: Having a fully functional feedback loop system helps meet anti-spam or data protection regulations.

• Gathers insights: FBLs offer insights into content performance and list hygiene.

For ISPs and recipients  

• Reduces unwanted mail: Providing a FBL ensures that you filter out unwanted messages. It ensures users’ inboxes contain more relevant messages.

• Promotes transparency: Providing a feedback mechanism for user complaints can resolve the issues quickly for a better user experience.

• Supports anti-spam measures: A FBL helps ISPs identify legitimate from malicious senders.

Example scenario  

Let’s say a retail brand sends out a promotional email to 100,000 subscribers.

Out of these emails, 150 recipients click “Report Spam” on the message in their inboxes.

• Without a feedback loop:
  The brand wouldn’t know who complained, and those recipients may continue receiving unwanted emails—causing more complaints over time and damaging the sender’s IP reputation.

• With a feedback loop:
  The ISPs where those complaints occurred (e.g., Zoho Mail, Gmail, Yahoo, Microsoft) send ARF reports back to the brand’s ESP. The system automatically unsubscribes those 150 users, keeping the complaint rate low and the brand’s reputation safe.

What do complaints through feedback loops denote?

• Poorly targeted emails: Complaints could mean that your emails are being sent to the wrong audience.

• Lack of easy unsubscribe options: Users click “Report Spam” when they can’t find an unsubscribe link or when the link doesnt work.

• Frequency fatigue: Sending too many emails too often overwhelms the recipient.

• Misleading subject lines or content: Prompts users to report emails as deceptive even though the content itself might have been relevant to them.

• List acquisition problems: Purchased or outdated email lists or addresses often cause higher complaint rates.

Feedback loop requirements  

The sender ISP has to be a part of the recipient ISP’s feedback loop program in order to receive the complaints. Most ISPs have a unique FBL requirement but most common expectations include:

• Domain ownership

• Dedication reporting address (abuse@abcbrand.com)

• Authentication (SPF, DKIM, PTR)

• Good sender reputation