Microsoft 365 Alert – Service Degradation – Microsoft Teams – Some users may receive Microsoft Teams meeting invitations as “not supported calendar message.ics” attachments – RESOLVED

01/04/2026 8:37:00 AM

NHSmail Reference: INC46787819

Microsoft Reference: TM1266678

Issue Status: RESOLVED

Issue Description: Users may have received Microsoft Teams meeting invitations as “not supported calendar message.ics” attachments.

Current Update: 01/04/2026 8:37:00 AM– Microsoft has identified a regression was introduced with a recent feature implementation for meeting join link validations, which is leading to this issue. While we continue to investigate what led to this impact within the feature, they have disabled the feature to bypass the path of the regression and confirmed this has addressed the problem.

Scope of impact: This issue may have affected some users receiving Microsoft Teams meeting invitations

Root cause: A recent feature implementation for meeting join link validations introduced a regression that led to this impact.

Next steps: Microsoft are continuing to review the specifics of the feature update along with the user reports of impact to assess areas for improvement that will help us to develop and redeploy the feature without introducing impact to service functionality. Based on our findings from understanding what led to this regression, they will implement further measures to bolster our feature deployment testing and validation phases to prevent similar issues from occurring in the future