Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to view on-premises or cross-tenant free/busy availability when scheduling meetings – RESOLVED

11/05/2026 09:07:00 PM

NHSmail Reference: INC46822039

Microsoft Reference: EX1304825

Issue Status: RESOLVED

Issue Description: Users may be unable to view on-premises or cross-tenant free/busy availability when scheduling meetings.

More info: Cross-tenant or on-premises free/busy lookups via the Outlook Scheduling Assistant fail for attendees in a specific domain. As a result, availability consistently appears as “Unknown,” preventing effective meeting scheduling.

Final Update: 12/05/2026 13:27:00 PM– Microsoft has received confirmation from several users who initially reported the issue that the fix was successful and the impact is remediated.

Scope of impact: Impact is specific to some users receiving inbound Microsoft Teams calls notifications when display names contain diacritics.

Root cause: A prior fix addressing corrupted text appearing when character encoding fails in call titles has unintentionally corrupted valid UTF-8 special characters in display names, causing improper character rendering in inbound call notifications and resulting in impact.

Next steps: Microsoft are further reviewing the recent update to understand how the new authentication pathway was incorrectly enabled, and to understand what prevented it from being detected in our update testing and validation procedures, which will allow us to prevent similar issues in future updates.