How to Improve Email Deliverability for Microsoft Outlook and Office 365 Recipients

Zuhaib A. · 2026-07-20T14:16:59.909Z

Hi there, I need some guidance regarding email deliverability. Over the last few weeks, my emails have been going to spam, specifically for Microsoft recipients (Outlook/Office 365). Could you please advise me on the best approach to resolve this issue? Thanks!

2 comments

· Sorted by Oldest

Shriya N.
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Hey Zuhaib A., feel free to ask this in 🔒[private feed] too!
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Md R.
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Yeah, MS-specific spam-foldering (versus Google delivering fine) is usually one of three failure modes. Which one you're in depends on your setup - quick check first: 1. What's your sending stack? M365 mailboxes direct, dedicated IP through a relay (SendGrid / Postmark / Amazon SES), or a shared-IP sequencer (Instantly / Smartlead / Apollo / Reply.io)? 2. What does your DMARC aggregate report show for MS-side deliveries? rua reports break out by receiving domain - MS-side pass/fail rates tell you whether it's an authentication alignment problem or a pure reputation problem. 3. Is it consumer inboxes or corporate tenants? Are you getting filtered at consumer addresses (@outlook.com / @hotmail.com / @live.com) or at corporate Office 365 domains? While you're pulling that, three things you can check now: **SNDS / JMRP (for consumer mail).** If you're hitting consumer junk folders, check your IP health at Microsoft's Smart Network Data Services. Heads up: MS overhauled the portal in June, it now lives at substrate.office.com/ip-domain-management-snds/SNDS (old URL deprecated). JMRP complaint feeds went header-only ARF at the same time - sender address redacted, message body stripped, so any tooling built against the old body-included format is broken. If you see a recent complaint-rate spike, that's likely your cause - MS spam-folders aggressively above ~0.3% complaint rate. **EOP + Delist Portal (for corporate B2B).** If you're getting filtered at corporate Office 365 tenants, SNDS won't reflect it - that's Exchange Online Protection filtering. Check whether your sending IP has been flagged on the enterprise blocklist and needs clearing via the Microsoft 365 Anti-Spam IP Delist Portal at sender.office.com. **MS SmartScreen on content.** MS inbound filters are more aggressive than Google on B2B cold-email content signals. In the last 30 days did you change anything about URL density per email, tracking-domain redirects (especially shared sequencer tracking domains), image count, or subject-line patterns? SmartScreen retrains on those shifts quickly. Immediate mitigation while you diagnose: cut your total volume to Microsoft destinations by half for two weeks. Not a permanent fix, but it stops the reputation drop from compounding while you find the root cause. Happy to look at a message-trace header or a rua sample if you drop it here or DM - the specific pattern usually surfaces from those first few data points.
2

Shriya N.
·
·
Hey Zuhaib A., feel free to ask this in 🔒[private feed] too!
✅1
Md R.
·
·
Yeah, MS-specific spam-foldering (versus Google delivering fine) is usually one of three failure modes. Which one you're in depends on your setup - quick check first: 1. What's your sending stack? M365 mailboxes direct, dedicated IP through a relay (SendGrid / Postmark / Amazon SES), or a shared-IP sequencer (Instantly / Smartlead / Apollo / Reply.io)? 2. What does your DMARC aggregate report show for MS-side deliveries? rua reports break out by receiving domain - MS-side pass/fail rates tell you whether it's an authentication alignment problem or a pure reputation problem. 3. Is it consumer inboxes or corporate tenants? Are you getting filtered at consumer addresses (@outlook.com / @hotmail.com / @live.com) or at corporate Office 365 domains? While you're pulling that, three things you can check now: **SNDS / JMRP (for consumer mail).** If you're hitting consumer junk folders, check your IP health at Microsoft's Smart Network Data Services. Heads up: MS overhauled the portal in June, it now lives at substrate.office.com/ip-domain-management-snds/SNDS (old URL deprecated). JMRP complaint feeds went header-only ARF at the same time - sender address redacted, message body stripped, so any tooling built against the old body-included format is broken. If you see a recent complaint-rate spike, that's likely your cause - MS spam-folders aggressively above ~0.3% complaint rate. **EOP + Delist Portal (for corporate B2B).** If you're getting filtered at corporate Office 365 tenants, SNDS won't reflect it - that's Exchange Online Protection filtering. Check whether your sending IP has been flagged on the enterprise blocklist and needs clearing via the Microsoft 365 Anti-Spam IP Delist Portal at sender.office.com. **MS SmartScreen on content.** MS inbound filters are more aggressive than Google on B2B cold-email content signals. In the last 30 days did you change anything about URL density per email, tracking-domain redirects (especially shared sequencer tracking domains), image count, or subject-line patterns? SmartScreen retrains on those shifts quickly. Immediate mitigation while you diagnose: cut your total volume to Microsoft destinations by half for two weeks. Not a permanent fix, but it stops the reputation drop from compounding while you find the root cause. Happy to look at a message-trace header or a rua sample if you drop it here or DM - the specific pattern usually surfaces from those first few data points.
2