**Microsoft** is currently addressing intermittent access problems affecting **Outlook** mobile and macOS users connecting to **Exchange Online**. These issues have been ongoing for several weeks. ### Root Cause and Mitigation Efforts The initial acknowledgement of this service issue, tracked under **EX1256020**, occurred last week. **Microsoft** identified a newly introduced virtual account as the root cause, with the problem initially reported to have begun on March 11. While initially marked as resolved on April 1, the incident has resurfaced under a new tracking number (**EX1268771**). According to **Microsoft**: "We've received reports from affected tenants that the impact scenario originally communicated through SHD EX1256020 is still ongoing. We're working to restart the Notification Broker service on affected portions of **Exchange Online** service infrastructure to remediate impact while we continue our analysis into the underlying root cause." The company further stated, "Impact may occur intermittently for some users accessing their **Exchange Online** mailboxes in the **Outlook** mobile apps or the new **Outlook** for Mac desktop client. This section may be updated as our investigation progresses." As of the latest update, the **Exchange Online** team is still actively investigating the root cause and implementing measures to prevent recurrence. ### Scope of Impact While **Microsoft** has not yet disclosed the geographical regions or the total number of users affected, the classification of this issue as an 'incident' indicates a critical service problem with significant user impact. ### Recent Exchange Online Issues This incident follows a recent mitigation of an **Exchange Online** outage that blocked access to mailboxes and calendars via **Outlook** on the web, **Outlook** desktop, **Exchange** ActiveSync, and other **Exchange Online** connection protocols. Around the same time, **Microsoft** addressed a separate issue causing sign-in problems with Office.com or **Microsoft 365 Copilot**, affecting the **Microsoft Copilot** desktop app, **Copilot** in **Microsoft Teams**, and **Copilot** in **Office** apps. Another **Exchange Online** service outage, which intermittently blocked email via the Internet Mailbox Access Protocol 4 (IMAP4), was resolved in January. A similar incident in November blocked **Exchange Online** access via the classic **Outlook** desktop client.