Update on custom domain guidance for Teams Event emails

Updated August 11, 2026: We are updating this post as a clarification. The change below was for WW customers only. This change does not apply to Sovereign Cloud environments. Customers in GCC, GCC High, and DoD must continue to configure a custom domain to use custom HTML editing and email template customization for Teams Events emails. We apologize for any confusion. We're clarifying our guidance around custom domain configuration for Teams event emails, based on customer feedback and recent questions. In a previous Message Center post (MC1234575 and MC1176301), we communicated that configuring a custom domain was required to use custom HTML editing for event emails. Based on customer feedback, this is no longer mandatory effecting immediately. When this will happen: Effective immediately How this affects your organization: Premium feature of custom HTML editing for Teams Events (Webinar and Townhall) emails is no longer blocked if your tenant does not have a custom domain configured. You can continue creating and sending event emails even without configuring a custom domain. However, we still strongly recommend configuring a custom domain for the best and most consistent email experience, especially for events sent to external audiences. Why we still recommend configuring a custom domain Configuring a custom domain helps: Provide clearer and more recognizable sender identity for recipients associated to your tenant Improve email deliverability and reduce the likelihood of messages being flagged or questioned Create a more trusted experience for attendees receiving event invitations, updates, and reminders If a custom domain is not configured, event-related emails will continue to leverage Microsoft provided domains, which can appear unfamiliar to recipients. What you can do to prepare: Review your tenant’s domain configuration in Microsoft 365 Consider configuring and validating a custom domain if your organization regularly hosts external or large-scale Teams events Update internal guidance to reflect that custom domains are recommended, but no longer required, for advanced email customization Documentation updates We are updating our documentation and guidance to clearly reflect: The removal of the custom-domain requirement for custom HTML editing When and why configuring a custom domain is still recommended You can learn more about managing email communications for Teams events on our learn page. We’re listening This update reflects direct customer feedback. We’ll continue monitoring support signals and feedback to further simplify and improve the event email experience.