Microsoft Addresses Service Issue Impacting Exchange Online Users

Microsoft is actively working to resolve an ongoing service issue that has intermittently hindered some users from accessing their cloud-based Exchange Online mailboxes through Outlook mobile and Mac desktop clients since Thursday.

Following an investigation into the incident (identified as EX1256020), Microsoft determined that the main issue stemmed from the introduction of a new virtual account.

Efforts to address the problem by restarting the affected infrastructure proved unsuccessful, prompting Microsoft to initiate work on reverting the change as a potential long-term solution to mitigate the impact.

“This issue may intermittently affect users trying to access the Exchange Online service via Outlook mobile apps or the new Outlook for Mac desktop client,” Microsoft stated.

Further assessment confirmed that the introduction of a new virtual account within the Exchange Online service was the cause of the disruption. To resolve the issue, Microsoft is disabling the change across affected environments and will provide a timeline for resolution once available.

While specifics on the regions or number of affected users were not disclosed, Microsoft categorized this service interruption as an incident, typically reserved for critical service issues with noticeable user impact.

A week prior, Microsoft tackled another Exchange Online outage that was impeding customers’ access to mailboxes and calendars via various Outlook platforms and Exchange Online connection protocols.

On the same day, a separate issue affecting Office.com or Microsoft 365 Copilot web sign-in access was resolved, attributed to a high volume of traffic impacting Microsoft Copilot desktop app, Copilot in Microsoft Teams, and Copilot in Office apps.

Microsoft also dealt with Exchange Online service outages in January and November, which intermittently blocked email access via IMAP4 and the classic Outlook desktop client, respectively.

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