Microsoft 365 Alert – Service Degradation – Microsoft Copilot (Microsoft 365) – Users’ draft generation prompts to Copilot may not have completed in the classic Outlook desktop app Build 2605 – RESOLVED

28/05/2026 08:37:00 AM

NHSmail Reference: INC46836962

Microsoft Reference: CP1324075

Issue Status: RESOLVED

Issue Description: Users’ draft generation prompts to Copilot may not have completed in the classic Outlook desktop app Build 2605.

More info: While Microsoft were focused on remediation, users may have prompted Copilot through the new Outlook app or Outlook on the web to bypass the impact.

Current Update: 28/05/2026 09:48:00 AM – Microsoft has confirmed that the impact resulted from a recent feature code upgrade intended to enhance text processing capabilities by enabling Markdown in Copilot when building Drafts, which introduced a code error. They have reverting this feature upgrade for all affected users, which has mitigated the impact. However, users will need to restart the classic Outlook app to have the mitigation applied.

Scope of impact: This issue may have affected all users who were attempting to generate a draft with a Copilot prompt in the classic Outlook desktop app on Build 2605.

Next Steps: Microsoft are reviewing the code error that was introduced with the feature upgrade to identify how it led to this impact. This assessment will allow them to develop a solution that will prevent impact from being reintroduced upon the feature being released again, as well as to help us isolate areas for improvement in their testing and validation phases to prevent similar future occurrences.