How to Fix Your Microsoft 365 Sender Reputation

By Henry Timmes · Email Deliverability Consultant · Named contributor to RFC 7489 & RFC 9989 (DMARC)

Microsoft 365Sender ReputationDeliverability

Henry Timmes Email Deliverability Consultant · Named contributor to RFC 7489 & RFC 9989 (DMARC)

The repair sequence that actually works - in the order that matters.

What Microsoft Sender Reputation Is

Microsoft keeps a running judgment of how trustworthy your sending IPs and your From domain are, built from volume, consistency, complaint rate, spam-trap hits, authentication results and recipient behavior. That judgment decides whether your mail inboxes, junks, or is rejected outright. Reputation is earned slowly and lost quickly.

The Repair Sequence

Reputation repair only works in order. Doing step four before step one wastes weeks.

Keeping It Once You've Got It

Reputation is not a one-time fix. Keep complaint rates low, keep the list clean, keep volume steady, and monitor SNDS and your DMARC reports so you catch a slide before Microsoft does. If you send through multiple IPs or domains, watch each one - a single bad stream can drag down the rest.

Frequently Asked Questions

How do I check my Microsoft sender reputation?

If you control your sending IPs, enroll in Microsoft Smart Network Data Services (SNDS) to see complaint rates, trap hits and filter results. Your DMARC aggregate reports and your own bounce/complaint logs fill in the rest.

How long does it take to rebuild Microsoft reputation?

With authentication and list issues fixed and steady, low-complaint sending, reputation typically recovers over a few weeks. There is no instant reset - Microsoft needs consistent good behavior to re-trust you.

Can Microsoft reputation be fixed without reducing volume?

Sometimes, but if complaints or traps are driving the problem, cutting back to your most engaged recipients while you repair is usually the fastest route back.

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