Microsoft Exchange Online | SMTP onboarding to App RBAC

Microsoft Exchange Online will enable admins to assign the SMTP.SendAsApp role to applications via App RBAC, allowing group-based or scoped mailbox access. This replaces manual per-mailbox permissions, simplifying OAuth SMTP client onboarding. Rollout begins November 2025, with no end-user impact. Prepare by planning group-based access and updating documentation.

[Introduction]

We're simplifying how organizations grant applications permission to send email on behalf of mailboxes. Today, customers must manually assign permissions to each individual mailbox using PowerShell, which is time-consuming and inefficient. With this new capability, admins can assign the SMTP.SendAsApp role to an app through App Role-Based Access Control (RBAC), enabling group-based or scoped access to mailboxes. This simplifies onboarding for SMTP clients using OAuth and provides a scalable, secure, and modern approach to managing mailbox access.

This message is associated with Microsoft 365 Roadmap ID 498356.

[When this will happen:]

• General Availability (Worldwide): We will begin rolling out early November 2025 and expect to complete by late November 2025.

[How this affects your organization:]

Who is affected:

• Admins managing SMTP AUTH clients using OAuth in Exchange Online.

What will happen:

• Admins can assign the SMTP.SendAsApp role to applications via App RBAC.
• This enables group-based or scoped access to mailboxes.
• Eliminates the need for per-mailbox permission assignments.
• Streamlines onboarding for SMTP clients using OAuth.
• No changes to end-user experience.

[What you can do to prepare:]

• Prepare to create security or distribution groups for mailboxes requiring access.
• Plan for migration from per-mailbox permissions to group-based RBAC assignments.
• Communicate this change to your helpdesk or support teams.
• Update internal documentation if you currently detail mailbox permission onboarding.
• Review onboarding documentation: Authenticate an IMAP, POP or SMTP connection using OAuth | Microsoft Exchange | Microsoft Learn (https://learn.microsoft.com/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth)
• Documentation will be updated November 1^st  

[Compliance considerations:]

No compliance considerations identified, review as appropriate for your organization.