Microsoft 365 Alert : Service Degredation – Exchange Online – Some users’ offline address book (OAB) in the Outlook desktop client is out of date and slow to update – RESOLVED

07/12/2022 08:35:00 AM (GMT)

NHSmail Reference : INC33197132

Microsoft Reference : EX481205

Issue Status : RESOLVED

Issue Description : Some users’ offline address book (OAB) in the Outlook desktop client is out of date and slow to update.

More info : Users’ OAB in the Outlook desktop client is out of date and slow to update. The OAB isn’t automatically updating and takes up to 16 hours for some users.

Scope of impact : Any users accessing the OAB from the Outlook desktop client may be affected.

Final Update : 19/01/2023 11:30:00 AM – As expected, Microsoft review of 503 errors has confirmed they have reduced drastically after implementation of our fix and as user clients continued updating, and impact has been successfully remediated.

Root cause : An issue in the core authentication infrastructure is resulting in a large burst of traffic to the authentication services, which is causing the service to perform below acceptable thresholds.