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Access Issues for Microsoft Exchange Online Mailboxes

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On March 1, 2023, at ~11:56 AM EST, Microsoft communicated via tweet (@MSFT365status) that they were investigating an issue in which users were unable to access Microsoft Exchange Online mailboxes.

Microsoft provided service incident number EX52202 for system admins to refence in the Microsoft Admin Center.



Earlier in the day, Microsoft also reported a service incident, MO521925, which impacted the APAC region and involved users unable to access some Exchange Online services and Microsoft Teams.

As to the new service incident EX522020, Microsoft then communicated via tweet additional details as to mailbox access issue, namely the error message users were receiving: "550 5.4.1 Recipient address rejected: Access denied,"  However Microsoft's investigation was ongoing and no fix was announced at this time.



At approximately 1:30 PM EST, about 90 minutes from their first message as to this service incident, Microsoft was indicating a recovery of services for most of the impacted areas.  But it should be noted that at this time Microsoft had still not identified a cause.



A follow-up tweet just 20 minutes later had Microsoft back pedaling a bit, as the original mailbox access issues persisted.  Microsoft was now confirming that their investigation, and efforts to remediate, were continuing at this time.



By 3:00 PM EST, Microsoft was communicating that some remediation efforts were in place.  Microsoft was at this time routing Exchange Online Protection (EOP) traffic away from impacted infrastructure.  Once completed with their rerouting of the EOP traffic, Microsoft then would reach out to affected users to begin confirming resolution.



Many Twitter responses from the community at this time were still confirming that the bounces and related mailbox access issues continued.

But by 4:00 PM EST, Microsoft communicated that the issue was resolved.





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