Microsoft investigates Exchange Online mailbox glitch

Microsoft first tweeted at 4:56 pm Wednesday about the issue; said it was resolved hours later

Some users of Microsoft Exchange Online were unable to access mailboxes through any connection method, Microsoft reported Wednesday.

Microsoft first tweeted at 4:56 pm GMT on Wednesday about the issue, also called EX522020.

"Users are reporting receiving an error including ‘550 5.4.1 Recipient address rejected: Access denied' and we are investigating further," Microsoft tweeted.

Later, at At 6:23 pm, Microsoft tweeted, "Our telemetry indicates that the service has largely recovered. We're continuing to investigate to determine the root cause and whether additional action is required."

Microsoft said at 7:58 pm that it was "in the process of routing EOP traffic away from what appears to be the affected infrastructure as a potential mitigation strategy. More details can be found in the admin center under EX522020."

By 8:59 p.m. ET, the problem was resolved. Microsoft said in a Twitter post.

"We've confirmed that rerouting EOP traffic to alternate infrastructure has resolved the user impact," the company said. "More details can be found in the admin center under EX522020."

The mass adoption of cloud computing tools means occasional but short-lived technical issues for IT professionals.

Microsoft-specific issues this year include an outage in January with Teams and Microsoft 365 and a separate outage that same month for multiple Microsoft 365 services including Teams and Outlook in North America.

This article first appeared in CRN