There are several potential reasons for Microsoft delivery issues. Here’s how to diagnose and fix them:
First, check your metrics in Email Signals:
If your bounce rate is above 2%, you’ll need to clean your lists.
If spam complaints are above 0.1%, review your content and opt-in practices.
Look at your delayed rates to Microsoft domains.
Check Message Events for specific Microsoft bounce codes.
[Optional with Inbox Tracker] Review reputation using SNDS or GPT.
Next, review any recent changes:
Have you sent more email than usual?
Did you change your email content?
Are you mailing to new lists?
Did you modify your authentication settings?
To resolve the issue:
Verify your authentication (SPF, DKIM, DMARC) in Email’s Domains section.
Remove inactive subscribers (no engagement for 6+ months).
Stop sending to bounced addresses.
Process unsubscribes immediately.
Keep your sending volume consistent.
Include clear unsubscribe links.
Use clear subject lines.
Include your physical mailing address.
Contact Email Support if:
You’ve completed all these steps.
Your metrics are within normal ranges.
Issues continue for more than 48 hours.
You see unusual bounce codes.
You need SNDS data for your dedicated IPs.
Most blocks clear automatically within 24-48 hours if you follow good sending practices.
