GoKawiilMicrosoft is working to address a widespread service issue affecting the mail flow pipeline for Exchange Online customers across North America and Germany.
The company first acknowledged this incident (tracked under EX1331830) at 10:33 EDT, when it began investigating a stream of reports from users on social media.
Some affected users are seeing temporary SMTP deferral errors, stating "The maximum number of concurrent connections per resource forest has exceeded a limit, closing transmission channel," while others see "Connection was closed abruptly (SuspiciousRemoteServerError)}" messages.
Microsoft said these ongoing issues are affecting Exchange Online users trying to send or access their emails, resulting in extensive delays or failures, and that its engineers are currently reviewing reports to discover the root cause.
"Users are experiencing significant delays in sending and receiving email messages, with some email messages remaining undelivered for over an hour," the company said in an admin center service alert.
"We're reviewing additional reports from customers in the North America and Germany regions to further our understanding of the current impact scenario, to isolate error messages affected users are receiving, and to determine our next troubleshooting steps."
The company has also classified this service outage as an incident, which typically applies to critical service issues with noticeable user impact.
In April, Microsoft also resolved Exchange Online mailbox access issues that had intermittently affected Outlook mobile and macOS users for weeks, and an Exchange Online outage that prevented users from accessing mailboxes and calendars via Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.
More recently, on Monday, it addressed an outage that prevented Teams and Office for the web users from opening files, and another incident that prevented customers from setting up multi-factor authentication (MFA) or accessing the My Sign-Ins platform.
This is a developing story ...