JMRP and FBL explained: how to read complaint loops as a cold sender
JMRP and FBL are the only direct complaint signals Microsoft and Yahoo provide. Most cold senders never see them.
Rejwan Nirob·Feb 26, 2026·5 min readJMRP (Junk Mail Reporting Program) is Microsoft's complaint feedback loop. FBL (Feedback Loop) is the equivalent from Yahoo, AOL, and a handful of others. Both deliver one signal - a recipient hit "report spam" on your message - and both are essential reading for any sender with sustained volume.
Why complaint loops matter
The single fastest way to lose sender reputation is a sustained complaint rate. Above 0.3% complaints, Microsoft starts aggressive filtering. Above 0.5%, you are deep in the spam folder. JMRP gives you the per-recipient detail to identify who is complaining, on which campaign, from which mailbox - so you can suppress and adjust before the reputation damage compounds.
Who can register
JMRP and FBL are typically restricted to senders who own the sending IP. Shared-IP senders rarely get direct access - their provider receives the reports and forwards aggregate data. Dedicated SMTP senders register directly under their IP block.
How to act on the data
- Suppress every complaining recipient immediately - they will not engage again
- Track complaint rate per campaign - a single bad campaign can drag a whole month
- Track complaint rate per mailbox - one bad mailbox is the usual culprit
- Investigate spikes within 24 hours - complaint reputation decays slowly
Lee SMTP (coming soon) registers JMRP and Yahoo FBL on every dedicated IP automatically. Reports surface in the dashboard with per-mailbox breakdown.
Join the waitlistFrequently asked
What is JMRP for email senders?
JMRP (Junk Mail Reporting Program) is Microsoft's complaint feedback loop. When a recipient on Outlook.com, Hotmail, or Live.com hits "Report Junk", JMRP forwards a copy of that complaint to the sender so they can suppress the recipient and trace which campaign and mailbox triggered the complaint. Essential for any sender with sustained Microsoft volume.
What is the difference between JMRP and FBL?
JMRP is Microsoft-specific (Outlook, Hotmail, Live). FBL (Feedback Loop) is the equivalent from Yahoo, AOL, and a handful of others. Both deliver the same signal - a recipient marked your message as spam - and both should be registered for any production-scale cold-email operation.
Can I register JMRP if I am on a shared sending IP?
Usually not. JMRP and FBL are typically restricted to senders who own the sending IP. Shared-IP senders rarely get direct access; their provider receives the reports and forwards aggregate data. Dedicated SMTP senders register directly under their IP block.
What complaint rate triggers Microsoft to filter my sends?
Above 0.3% complaints, Microsoft starts aggressive filtering. Above 0.5%, you are deep in the spam folder. JMRP gives per-recipient detail so you can identify who is complaining, on which campaign, from which mailbox - and suppress before the reputation damage compounds.