The one-sentence version#
Feedback loops (FBLs) are programs run by mailbox providers (Microsoft JMRP, Yahoo CFL, Comcast, and others) that send you a copy or notice whenever a recipient marks your message as spam.
Why you should care#
Complaints are the strongest negative signal. FBLs let you suppress complainers immediately and detect problem campaigns before reputation collapses.
The mental model#
Think of complaint feedback loops as a contract between you and the mailbox providers receiving your mail. You publish or configure something they can check; they check it on every message; the result feeds their decision about where your message lands. Everything below is about making that check pass consistently.
Your first setup, step by step#
- Register your sending IPs and domains with each provider's FBL.
- Route FBL messages to an automated parser.
- Suppress every complainer from all future marketing.
- Report complaint rate per campaign and per acquisition source.
Words you will see#
- Mailbox provider: Gmail, Microsoft, Yahoo, Apple, and the corporate gateways that decide where mail lands.
- Authentication: proof that a message is from who it says it is (SPF, DKIM, DMARC).
- Reputation: the provider's running score of your domain and IP.
- Placement: whether a message reaches the inbox, spam, or is rejected.
Common mistakes#
- Registering but never processing the reports.
- Gmail has no traditional FBL; use Postmaster Tools spam rate instead.
Frequently asked questions#
Does Gmail offer a feedback loop?
Only an aggregate one via Postmaster Tools using the Feedback-ID header. Gmail does not return individual complaints.