Background
Microsoft 365 employs various outbound delivery channels for sending emails to external recipients. In specific scenarios, forwarded or relayed messages are processed through a specialized relay pool, particularly when the destination should not recognize Microsoft 365 as the original sender. Additionally, lower-quality messages are routed through Microsoft's high-risk delivery pool. For further details, please refer to the article on Outbound Delivery Pools - Microsoft Defender for Office 365.
For customers utilizing Microsoft 365 in conjunction with Trend Micro Email Security or Trend Vision One Cloud Email Gateway Protection, emails from both Microsoft's relay and high-risk delivery pools are currently routed to the respective relay systems of these Trend Micro solutions.
Upcoming Change
Trend Micro Email Security and Trend Vision One Cloud Email Gateway Protection will begin implementing a dedicated channel for routing emails from Microsoft 365's relay and high-risk delivery pools. This change is aimed at preventing the blocking of their IP addresses.
The said change will be implemented first on the India (IN) site. Rollouts to other regions will follow, with separate announcements to be sent once the schedules are finalized.
Important Notes
- The IP addresses utilized by this dedicated channel will not be included in the SPF records for Trend Micro Email Security and Trend Vision One Cloud Email Gateway Protection.
- Emails sent through this channel will not have DKIM signatures applied but will still be scanned by our service.
Deployment Schedule and Scope
| Site | Date/Start Time | Date/End Time |
|---|---|---|
| IN | 2025-10-20 10:00:00 (GMT +8) | 2025-10-20 12:00:00 (GMT +8) |
Service Downtime
There is no expected service downtime in this deployment.
Customer Impact
Emails transmitted via this dedicated channel may be rejected by destination servers due to the absence of SPF or DKIM validation.
If you experience any delivery issues, please reach out to Microsoft Support to explore options for avoiding the use of the high-risk or relay delivery pools.
For any questions or concerns, please contact your assigned Customer Service Manager or Trend Micro Technical Support.