Microsoft Exchange Online service change causes email access issues

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HomeNewsMicrosoftMicrosoft Exchange Online service change causes email access issues

Microsoft Exchange Online service change causes email access issues

By Sergiu Gatlan

March 23, 2026
08:17 AM
1

Microsoft is working to address an ongoing service issue that has intermittently prevented some users from accessing their cloud-based Exchange Online mailboxes via Outlook mobile and Mac desktop clients since Thursday.
After investigating the incident (tracked under EX1256020), Microsoft found that the root cause was a newly introduced virtual account.
On Saturday, began working to revert the change as a possible long-term solution to mitigate the impact, after failing to address the problem by restarting the affected infrastructure.
"This issue may intermittently impact some users who are attempting to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client," Microsoft said.
"After further assessment, we've confirmed that the identified change within the Exchange Online service intended to introduce a new virtual account resulted in impact. To remediate this issue, we're disabling the change across the affected environments. Once available, we'll provide a resolution timeline."
While Microsoft didn't share which regions or how many users were affected, it flagged this service outage as an incident, which usually applies to critical service issues with noticeable user impact.
One week ago, Microsoft addressed another Exchange Online outage that was preventing customers from accessing their mailboxes and calendars via Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.
On the same day, it fixed a separate issue causing Office.com or Microsoft 365 Copilot web sign‑in access problems due to what the company described at the time as "a high volume of traffic," affecting the Microsoft Copilot desktop app, Copilot in Microsoft Teams, and Copilot in Office apps.
Microsoft also mitigated an Exchange Online service outage in January that intermittently blocked email via the Internet Mailbox Access Protocol 4 (IMAP4) and a similar incident in November that blocked Exchange Online access via the classic Outlook desktop client.

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Related Articles:
Microsoft Exchange Online outage blocks access to mailboxesMicrosoft fixes Outlook bug blocking access to encrypted emailsMicrosoft: Outlook for iOS crashes, freezes due to coding errorMicrosoft shares fix for Windows C: drive access issues on Samsung PCsMicrosoft: March Windows updates break Teams, OneDrive sign-ins

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Sergiu Gatlan
Sergiu is a news reporter who has covered the latest cybersecurity and technology developments for over a decade. Email or Twitter DMs for tips.

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Throwdown - 1 hour ago

Their devs should stop relying on copilot, it sucks.

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Microsoft is currently experiencing an ongoing service issue impacting access to Exchange Online mailboxes for some users, as reported by Sergiu Gatlan on March 23, 2026. The disruption, tracked under EX1256020, primarily affects users accessing the service through Outlook mobile apps and the new Outlook for Mac desktop client. Investigations revealed that the root cause stemmed from a recently introduced virtual account change. Despite attempts to resolve the issue by restarting impacted infrastructure, the problem persisted, leading Microsoft to disable the change as a long-term mitigation strategy.

The company acknowledged that the impact was significant enough to classify it as an incident, though specific details regarding the scope of affected regions and users remained undisclosed at the time of reporting. This incident follows a similar outage experienced one week prior, which prevented access to mailboxes across various platforms including the Outlook web interface, Outlook desktop, Exchange ActiveSync, and other connection protocols. A separate outage on the same day addressed problems with Office.com and Microsoft 365 Copilot web sign-ins due to a high volume of traffic.

Furthermore, this is not the first time Microsoft has faced Exchange Online service disruptions. Previous incidents occurred in January and November, briefly blocking email access via IMAP4 and the classic Outlook desktop client, respectively. The repeated outages highlight potential stability concerns with recent service changes. Microsoft’s response includes a commitment to provide a resolution timeline once the corrective measure is implemented. The company’s actions demonstrate a reactive approach as they addressed a problem originating from a newly introduced virtual account.