Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to access their mailboxes through multiple connection methods in Exchange Online – RESOLVED

Announcements Arpan Das

29/07/2025 08:53:00 AM

NHSmail Reference: INC46590778

Microsoft Reference: EX1123238

Issue Status: RESOLVED

Issue Description: Users may be unable to access their mailboxes through multiple connection methods in Exchange Online.

More info: Impacted connection methods include but aren’t limited to:
– Outlook on the web
– Exchange ActiveSync
– Internet Message Access Protocol (IMAP)
– Messaging API (MAPI)

Final Update: 30/07/2025 09:03:00 AM – Microsoft’s have confirmed the memory allocation problem on a portion of infrastructure that facilitates Exchange Online access through multiple connection methods for the affected users was causing the impact. They have also verified impact has been remediated as service availability and service health have remained stable.

Scope of impact: Some users in Europe may be unable to access their mailboxes through multiple connection methods in Exchange Online.

Next Steps: Microsoft are reviewing performance data and trends on the affected infrastructure to help prevent similar impact from happening again.