💡 Our Technical Review in summary
Summary
- Microsoft has officially enforced the requirement that all custom HTML email templates for Teams Events must reference a verified custom domain within the Microsoft 365 tenant.
- This change aims to improve email deliverability, align with modern authentication standards (SPF/DKIM/DMARC), and reduce the risk of spoofing.
- The enforcement phase was completed on January 31, 2026, following the initial announcement in October 2025 (MC1176301).
Impact
- Targeted Users: Only organizations with Teams Premium licenses using custom HTML templates for Teams Events notifications are affected.
- Functionality Risks: Any custom templates that do not reference a verified domain may fail to send, lose custom branding, or revert to default formatting.
- Default Templates: Organizations using the standard, out-of-the-box Microsoft Teams email templates are not impacted by this change.
- Administrative Overhead: IT admins must ensure domain alignment between the email sender identity and the tenant’s verified domains to maintain template integrity.
Action Required
- Verify Domains: Navigate to the Microsoft 365 Admin Center to confirm that the domain intended for product notifications is fully verified and active.
- Update Template Settings: Review and update Teams Events email template configurations to ensure the custom HTML points specifically to a verified domain.
- Propagation Period: Allow up to 12 hours for changes to propagate globally after saving the new domain configurations.
- Internal Communication: Notify Teams Event organizers and template maintainers of this requirement to ensure any new templates created in the future follow the verified domain protocol.
- Validation: Send test event invitations to verify that custom branding and formatting are rendering correctly post-enforcement.
Microsoft Official Update
Service: N/A
Category: stayInformed
Severity: normal
[Introduction]
To ensure reliable delivery of Teams Events email notifications—and to protect organizations using custom HTML templates—we’re enforcing a requirement that all templates reference a verified custom domain in your Microsoft 365 tenant. This improves deliverability, reduces spoofing risk, and aligns with modern email authentication standards. As previously communicated in MC1176301 (October 2025), templates not configured with a verified domain may no longer function as expected after enforcement.
[When this will happen:]
Enforcement was fully rolled out January 31, 2026.
[How this affects your organization:]
Who is affected:
- Organizations with Teams Premium licenses.
- Organizations using custom HTML templates for Teams Events email notifications.
What will happen:
- Custom HTML templates must reference a domain verified in your Microsoft 365 tenant.
- Templates without a verified domain may stop working as expected once enforcement begins.
- Custom formatting or branding may fail without the required configuration.
- No impact for organizations using default templates.
[What you can do to prepare:]
- Verify or confirm ownership of the domain you want to use for product notifications in the Microsoft 365 admin center.
- Update Teams Events email template settings so your custom HTML references a verified domain.
- Allow up to 12 hours for global propagation after saving.
- Update internal documentation and notify Teams Events owners or template maintainers.
Learn more:
Configure domain selection for Microsoft 365 product notifications
[Compliance considerations:]
No compliance considerations identified, review as appropriate for your organization.
