Exchange Online Outage Blocks Access to Outlook Mailboxes

Microsoft announced earlier today it is looking into an Exchange Online service outage that is preventing users from accessing their emails via the old Outlook desktop client.

Microsoft first reported the event (recorded under EX1189820) at 09:57 AM UTC, and according to user reports on the DownDetector outage monitoring platform, it is also creating server connection and login problems.

In classic Outlook, users may be unable to connect to their Exchange Online mailbox. Microsoft stated that they are actively investigating the root cause of the connectivity failures which was experienced.

Microsoft further said that the Impact is specific to users located in the Asia Pacific and North America regions attempting to connect to their Exchange Online mailbox using the classic Outlook experience.

Microsoft’s incident response teams are investigating service-side logs to determine the source of the connectivity and search issues.

Although Microsoft hasn’t disclosed how many users are affected however the issue has been marked as an “incident” in the admin center with a designation typically reserved for problems with substantial user impact.

As a solution, Microsoft recommends that impacted users access their mails using Outlook on the Web.

The Classic Outlook search issues which Microsoft is presently investigating the root cause of these connectivity failures, as well as a separate incident (EX1189768), which was reported on Thursday morning at 05:05 AM UTC and is causing search troubles for classic Outlook users.

“The impact is limited to those users trying to search on the original Outlook desktop client. “We are analysing service-side logs to determine the root cause and devise a mitigation strategy,” it added.

This comes after a severe DNS outage that affected Azure and Microsoft 365 services in late October, preventing users from logging into enterprise networks or accessing multiple applications and platforms.

It resolved another outage in early October that was preventing customers from accessing Microsoft Teams, Exchange Online, and the admin centre with Microsoft Entra single sign-on (SSO) login due to Multi-Factor login (MFA) difficulties.

And just less that twenty-four hours later, Microsoft addressed a second incident stemming from an Azure Front Door CDN failure that had brought down Microsoft 365 services for customers throughout Europe, Africa, and the Middle East.

The current issue follows multiple and several others but yet short-lived Microsoft service disruptions that have occurred throughout 2025.