Feedback Loop
Email MarketingAlso: FBL · Complaint Feedback Loop
Quick definition
A feedback loop (FBL) is a system some mailbox providers offer that tells a sender when a recipient marks their email as spam. It gives the sender the complaining address so they can suppress it before the complaint damages sender reputation further.
How it varies across Australia
Complaint rates that trip provider thresholds vary by mailbox provider, but Australian senders using shared or poorly warmed infrastructure tend to sit closer to those thresholds than senders on dedicated, well-managed sending domains.
See email deliverability benchmarks across Australian industries →What it actually means
A feedback loop works like a neighbour telling you your dog barked before they call the council. The mailbox provider is giving you a chance to fix the problem before it escalates into something that hurts your deliverability across the board.
Here's the mechanic. When a recipient clicks 'report spam' instead of unsubscribing, that action is a complaint. Mailbox providers that offer FBLs will forward a notification back to the sender, usually via an automated feed, containing the complaining address (sometimes hashed). The sender is expected to suppress that address immediately.
FBLs matter because complaint rate is one of the strongest signals feeding sender reputation. It sits alongside bounce rate, spam trap hits, and engagement metrics like open rate and click through rate. A rising complaint rate tells a mailbox provider your list quality or your segmentation is off, and inbox placement drops in response.
Not every provider offers an FBL, and not every sender qualifies for the ones that do. Access is usually gated by sending volume and requires the sender's Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) records to be correctly configured first.
A feedback loop is not a warning. It is the mailbox provider doing you a favour before it stops doing you any favours at all.
How it shows up
Feedback loop data shows up as a feed or report, not a dashboard metric most marketers check daily. It surfaces in your Email Service Provider (ESP) as automatic suppressions, or as a raw file from providers like the ones behind large consumer webmail platforms. The practical sign of a healthy feedback loop process is a suppression list that grows quietly in the background and a complaint rate that never climbs high enough to trigger provider throttling.
The Australian context
Australia's Spam Act 2003 already requires consent and a working unsubscribe mechanism, so a well run Australian sender should see relatively few complaints if list hygiene and segmentation are solid. Feedback loop data becomes the early warning system that catches problems before they become an ACMA complaint or a mass deliverability collapse across your sending domain.
Where people get this wrong
Related terms
Common questions
How do I get access to a feedback loop?
You register with the mailbox provider directly, usually through a postmaster portal. Most require correctly configured SPF and DKIM records and a minimum sending volume before they'll approve access. Each major provider runs its own separate registration process.
What should I do when I get a feedback loop notification?
Suppress the complaining address immediately across all sending lists, ideally through automation rather than a manual process. Then check whether that complaint came from a specific segment or campaign so you can address the underlying relevance problem.
Does a feedback loop stop all spam complaints?
No. It only reports complaints from mailbox providers that offer the feature and that you're registered with. Plenty of complaints happen at providers without an FBL, or get filtered before you ever see a notification.
How is a feedback loop different from a bounce?
A bounce means the email couldn't be delivered at all, either permanently or temporarily. A feedback loop notification means the email was delivered and the recipient actively marked it as spam. They're separate signals that both damage sender reputation.
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About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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