Microsoft 365 Alert – Service Degradation – Exchange Online – Users may have been unable to access their mailbox through Internet Message Access Protocol (IMAP) – RESOLVED

Announcements Sourav Nandi

16/06/2025 08:35:00 AM

NHSmail Reference: INC46555241

Microsoft Reference: EX1094472

Issue Status: RESOLVED

Issue Description: Users may have been unable to access their mailbox through Internet Message Access Protocol (IMAP).

More info: Users may have been unable to access their mailbox through IMAP.

Final Update: 16/06/2025 08:35:00 AM – Microsoft have confirmed after a period of monitoring service telemetry that impact has been remediated.

Scope of impact: Impact was specific to users who were served through the affected infrastructure.

Root cause: A section of mailbox database infrastructure that facilitates IMAP requests fell below our manageable service performance thresholds, resulting in impact.

Next steps: Microsoft are analyzing performance data and trends on the affected mailbox database infrastructure to help prevent this problem from happening again.