Microsoft Webinar emails suddenly ending up in spam

Hi @Jen,  

Welcome to the Microsoft Q&A forum. 

Thank you for providing such a clear summary of the issue. I completely understand how inconvenient it is when a reliable process suddenly experiences deliverability issues. 

Since Microsoft Teams generates these emails automatically, delivery can be impacted by recent updates to spam filtering logic on either your internal tenant or the recipients' mail systems. To help narrow this down further, could you clarify the following?

1. Are you seeing these emails land in spam for users within a particular organization, or are you receiving reports from people across many different services, including public ones like Gmail or Outlook?
2. Is there anything unique about the March webinars compared to previous months, such as a new organizer, updated branding, or different links in the description? 

Based on your information. I have outlined some steps; please follow the steps and kindly update me on the outcomes:

1/ Verify webinar-level settings 

• Confirm attendee emails are enabled: In the setup for each March webinar, verify that the "Enable attendee emails" toggle is turned on. If this was inadvertently disabled, no automated communications will be sent. 
• 
• Identify specific failures: Determine if the issue is isolated to a specific type of communication (e.g., only reminders) or if it affects registration confirmations and event updates as well. 

2/ Review content (for Teams premium users) 

If you are using Teams Premium and have customized your email templates or reminder schedules, try reverting to the default content temporarily. Sometimes, specific links or phrasing in a custom template can trigger external spam filters. 

3/ IT admin diagnostics 

If the settings appear correct, your IT administrator can perform more granular checks: 

• Run message traces: For internal recipients, an admin can use the Exchange Admin Center to see exactly why a message was flagged or quarantined. They can then mark these as "false positives" to improve future filtering. 
  • I recommend providing the Message trace in the new EAC in Exchange Online article to your IT admin so they can identify exactly why these webinar emails are being filtered or quarantined.
• Analyze email headers: Request that one affected recipient share the message headers of a "spammed" email. Your admin can analyze these to see which specific security check (SPF, DKIM, or DMARC) might be failing. 

If this issue persists across multiple external domains and only affects your March sessions, it is likely a service-side deliverability signal. In this case, I recommend opening a Microsoft 365 Support ticket via the Admin Center so they can review your specific tenant logs. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin. 

I hope this helps get your webinars back on track. Please let me know if you have any other questions or need assistance. 

I look forward to your thoughts on this.

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For Teams webinars, registration and reminder emails are sent by the Microsoft Dynamics 365 email delivery service. If these suddenly start going to spam for external recipients, the most likely cause is that the service’s sending IPs are no longer treated as allowed/trusted by recipients’ spam filters.

Use these steps to mitigate the issue on the Microsoft 365 side for your tenant and help recipients improve deliverability:

1. Allow Dynamics 365 webinar email IPs in your spam protection
   Webinar invitations and related emails are sent using the Dynamics 365 email delivery service. If your organization (or recipients’ organizations) has tightened external email policies recently, these messages can be quarantined or marked as spam. In your Microsoft 365 tenant, add the Dynamics email delivery IP ranges to the allow list in the default Connection filter policy:
   1. Go to the Anti-spam policies page in the Microsoft 365 Defender portal.
   2. Select Connection filter policy (Default) (do not tick the checkbox).
   3. In the flyout, under Connection filtering, select Edit connection filter policy.
   4. Under Always allow messages from the following IP addresses or address range, add the IP addresses used by the Dynamics email delivery service as documented in IP addresses that's used by the Dynamics email delivery service.
   5. Press Enter or select the suggested IP value, then Save.
   6. If prompted to enable customization, select Yes and wait for completion.
   7. If customization is disabled and you get an error:
      • Wait a few hours and try again adding one IP range at a time.
      • If still blocked, connect to Exchange Online PowerShell and run Enable-OrganizationCustomization, then add the remaining IP ranges and save.
   This reduces the chance that webinar emails are treated as spam within your own tenant. External customers’ organizations can perform similar allow-listing for those same IPs in their own spam solutions.
2. Confirm that the behavior is spam classification, not non-delivery
   Since users are receiving the messages in spam, this is a classification issue rather than a delivery failure. If any recipients report non-delivery or NDRs, have them:
   • Check Junk/Spam folders first.
   • If messages are missing entirely, their mail admins should review their own spam/connection filtering and ensure they are not blocking the Dynamics sending IPs.
3. Ask affected recipients to mark messages as not junk / safe
   For individual recipients whose clients support it (for example, Outlook), ask them to:
   • Move the webinar emails from Junk/Spam to Inbox.
   • Add the webinar sender address to their Safe Senders list. Over time, this can improve classification.
4. Understand the email types and timing (for validation)
   Teams webinars generate multiple email types (registration confirmation, pending approval, waitlist, rejection, cancellation, date/time updates, reminders, and “event recording available”). All of these are sent via the same underlying service. If all of them for March events are going to spam while older events were fine, it strongly suggests a change in spam filtering or reputation rather than a change in webinar configuration.
5. Coordinate with customers’ mail admins if this is tenant-wide for them
   If entire customer organizations report that all webinar emails are now spam:
   • Share with their mail admins that the messages originate from the Dynamics 365 email delivery service.
   • Provide them with the official public IP ranges for that service so they can add them to their own allow lists or adjust their spam thresholds.

If, after allow-listing the Dynamics email IPs and having recipients mark messages as not junk, emails still consistently land in spam, escalate through your email/security team to review message headers and spam verdicts in their filtering solution for further tuning.

References:

• Issues that affect Teams webinars
• Manage webinar emails in Microsoft Teams
• Troubleshoot email issues
• External senders - Troubleshoot email sent to Microsoft 365