Microsoft is investigating an ongoing outage preventing Exchange Online customers around the world from accessing their mailboxes or sending/receiving email.

Affected users are seeing “550 5.4.1 Recipient Address Rejected: Access Denied” errors when trying to send or receive messages, starting today at 13:11 UTC.

“We are investigating an issue preventing users from accessing their Exchange Online mailboxes through any sign-in method. Additional details can be found in the Service Health Dashboard under EX522020,” Microsoft tweeted earlier today.

Customers also report Twitter And Reddit that large percentages of email sent to Exchange Online mailboxes will not reach recipient mailboxes.

“We have identified a potential directory-based edge blocking (DBEB) issue that could contribute to the impact,” Microsoft said in a service health alert posted today at 5:22 p.m. UTC.

“We are looking at this alongside our existing diagnostic data to determine our next steps. The impact is specific to users who are served by the affected infrastructure in North America, Europe and the UK.”

DBEB Allows administrators to configure rejecting messages for invalid recipients and blocking all messages sent to email addresses not present in Microsoft 365 or Office 365.

While Redmond said 30 minutes ago that telemetry data indicated the service was starting to recover, a later update says further monitoring revealed the outage is still ongoing.

Our ongoing monitoring has indicated that the problem persists. We are continuing to investigate, and more details can be found under EX522020 in the admin center.

— Microsoft 365 Status (@MSFT365Status) March 1, 2023

Earlier today, Redmond also mitigated a second outage preventing some users in the Asia-Pacific region from accessing Exchange Online and Microsoft Teams services.

New global outage removed several Microsoft 365 services in late January, after a router IP address change caused packet forwarding issues between Microsoft wide area network (WAN) routers.

The list of services affected by last month’s outage included Microsoft Teams, Exchange Online, Outlook, SharePoint Online, OneDrive, Microsoft 365 Admin Center, Microsoft Graph, Microsoft Intune and several Microsoft Defender products.

This is a developing story…