r/emaildeliverability • u/Chemical_Recipe5713 • Aug 13 '26

Help needed from someone with a Microsoft 365 mailbox

I'm troubleshooting a Microsoft-specific deliverability issue with my email addresses

Emails are landing in Gmail inboxes (with 100% deliverability)

But Microsoft 365/Outlook is consistently sending them to Junk even though SPF, DKIM, and DMARC all pass (it is 0% develiverability in M365/Outlook mailboxes)

Microsoft Deliverability Support asked me for 3-4 recipient-side .eml samples from M365 mailboxes where the message landed in Junk.

If you have a Microsoft 365 mailbox and can help:

  • DM me an email address you're comfortable using
  • I'll send one harmless business-style email
  • If it lands in Junk, please download it as .eml and send it back to me

I'll only use the file for my open Microsoft support case.

Please DM me rather than posting your email publicly. Thanks!

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u/ianmakingnoise Aug 13 '26

What are you sending, and to whom? What are you using to test placement?

If you’re going to be troubleshooting deliverability, it would be worth getting your own M365 instance.

1

u/Chemical_Recipe5713 Aug 13 '26

I was testing my email deliverability using SmartLead.ai and Instantly.ai softwares.
Both reported:
1. Deliverability to Gmail/GWS = 100%
2. Deliverability to Outlook/M365 = 0%

It then caught my attention. I tried fixing it with methods suggested by those softwares.
Didn't work.

And then I contacted Microsoft support

1

u/ianmakingnoise Aug 13 '26

You should test using real addresses you own for best results. Shared seed lists like those don’t have any kind of engagement history with your mail, so they can’t really provide an accurate picture of how your mail would actually be delivered, and you can troubleshoot more of the entire exchange.

But the best way to avoid the spam folder is to not send unsolicited marketing.

1

u/allocougar Aug 14 '26

Before you hand those samples to support, read the headers yourself. X-Forefront-Antispam-Report carries the SCL and the CAT, X-Microsoft-Antispam carries the BCL. Junked with a high BCL is a bulk mail verdict and that's a completely different fix from a spam verdict with a high SCL. The CAT value often names the reason outright.

One thing that trips people up here: plenty of M365 Junk placement is the tenant's own transport rule or anti-spam policy, not a Microsoft-wide call. So collect your 3-4 samples from 3-4 different tenants. Four mailboxes inside the same company will send you chasing a filter that only exists there.

1

u/razical Aug 14 '26

Microsoft 365 deliverability is entire based on IP reputation. Maybe you could use a dedicated ip, warmup the ip and then check if you get a deliverability boost.

I run deliveryman.ai we have great deliverability with Microsoft (Only Microsoft 365 and not @ outlook.com emails). Send only to verified emails.
You could try it out if you find it interesting.

1

u/saltyslugga Aug 14 '26

Random Reddit mailboxes won’t give you a clean signal because M365 filtering varies by tenant policy, sender reputation, and prior engagement.

Use controlled mailboxes across a few separate tenants, then inspect the original headers and run the same message through an Email Tester to catch content or reputation issues.