MC1515932 - External Recipients Banner on Outlook Mobile

Microsoft 365 Message Center announcement MC1515932.

MS Message Center's Summary

Microsoft is introducing a visual warning banner in Outlook Mobile that appears when external attendees are included in meetings. Global rollout begins in late October 2026 and concludes by late November 2026. This feature aims to reduce accidental data leakage by alerting users before they send calendar invitations outside the organisation. Administrators should review internal support materials to prepare help desk staff for user queries regarding the new banner.

Administrator impact
No direct administrator action is required.
End user impact
Users will see a warning banner in Outlook Mobile when external participants are added to meetings.
Importance
2/10: This is a standard informational feature rollout with no administrative configuration or mandatory action required.

Microsoft Summary

Outlook Mobile will display a banner warning when external attendees are added to meetings, rolling out worldwide from late October to late November 2026. This helps prevent accidental sharing with external recipients. No action or compliance changes are required.

Message Center ID
MC1515932
Category
stay Informed
Severity
normal
Services
Exchange Online
Tags
New feature, User impact
Published
2026-10-19
Last updated
2026-10-19
Expires
2026-12-30

[What and Why:] When you add an attendee outside your organization to a meeting, Outlook will display a banner warning you that external recipients are included. [Rollout Schedule:] General Availability (Worldwide): We will begin rolling out on late October 2026 and expect to complete by late November 2026. [Impact on Your Organization:] Helps users avoid accidentally inviting external attendees to meetings by clearly identifying recipients outside their organization, reducing the risk of unintentionally sharing sensitive information. [Action Required/Recommendations:] No action is required [Compliance considerations:] No compliance considerations identified. Review as appropriate for your organization.