Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be intermittently unable to access their Exchange Online mailboxes via any connection method – RESOLVED

06/09/2023 09:00:00 AM (GMT)

Microsoft Reference : EX673494

Issue Status : RESOLVED

Issue Description : Some users may be intermittently unable to access their Exchange Online mailboxes via any connection method.

More Info : Some users may be intermittently unable to access their Exchange Online mailboxes via any connection method

Final Update : 06/09/2023 09:00:00 AM – Upon further investigation, Microsoft have determined that a code change made in a portion of infrastructure which facilitates mailbox access caused the infrastructure to perform below acceptable performance thresholds, resulting in impact. They’ve manually reverted the offending code change, after which their internal telemetry system indicated that service availability has returned to normal health and the issue has been resolved.

Scope of impact : Impact may have occurred for some internal Microsoft users only.

Root cause : A code change made in a section of infrastructure which facilitated mailbox access caused the infrastructure to perform below acceptable performance thresholds, resulting in impact

Next steps : Microsoft are reviewing their recent code change testing and validation within Exchange Online service infrastructure aimed at eliminating potential similar impact to users accessing their mailboxes via any connection method in the future.