Microsoft Fixing Outlook Email Problems Triggered by Exchange Online Issue

Microsoft is working to fix an Exchange Online issue that’s preventing some Outlook mobile users from accessing their emails and calendars. The problem, tied to Hybrid Modern Authentication (HMA), first appeared on August 17 and has been causing significant disruptions.

Folks at Bleeping Computer spotted that the incident is tracked under EX1137017 in the Microsoft 365 Admin Center. The bug apparently stems from a recent service change aimed at improving mailbox sync efficiency.

However, the change introduced unexpected behavior, triggering 12-hour delays for affected accounts. Microsoft explains that “some users may be unable to send or receive email from the Outlook mobile app on their devices.”

The company further notes:

A recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval.

Engineers in Redmond have since pushed out a fix to stop these sync jobs from getting quarantined. A previous attempt to cut the delay from 12 hours to one hour did not work, forcing Microsoft to roll out a more permanent solution.

While the company hasn’t revealed how many users or which regions are impacted, the situation is classified as a service incident, meaning user disruption is widespread enough to be noticeable. Moreover, you can also check our guide to fix Outlook not sending emails.

Teams’ issue is also under review

Not to forget, a separate service alert (TM1134507) highlights a problem with the Teams desktop app, where some users experience blank screens or freezes during meetings. Microsoft suggests affected users, particularly those running Intel driver version 32.0.101.69xx, switch to the Teams web app until a permanent fix is available.