Why Your Emails Reach Gmail but Not Microsoft 365

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

The same campaign inboxes at Gmail and junks at Microsoft. Here's why - and how to close the gap.

Why Gmail Says Yes and Microsoft Says No

Gmail and Microsoft weigh signals differently. Gmail leans heavily on recipient engagement - opens, replies, moving mail out of spam. Microsoft leans more on IP and domain reputation and on its own complaint data. A sender with good engagement but a young or thinly-used IP can clear Gmail easily and still be filtered by Microsoft.

So the split you are seeing is not random. It is the predictable result of two filtering philosophies, and it is the most common pattern I am called in to fix.

What the Split Tells You

If Gmail inboxes and Microsoft junks, you can usually rule out content and basic authentication as the primary cause - those would hurt you at Gmail too. The finger points at Microsoft-specific reputation: your IP, your domain history with Microsoft, and your complaint rate among Microsoft recipients.

How to Close the Gap

Confirm authentication passes and aligns, then focus on the Microsoft-only levers: enroll in SNDS and JMRP if you control your IPs, drive down complaints, clean Microsoft-domain addresses (outlook.com, hotmail.com, live.com and Microsoft-hosted business domains) especially hard, and rebuild reputation with steady volume.

Frequently Asked Questions

Why do my emails reach Gmail but not Microsoft 365 or Outlook?

Does this mean my content is fine?