Microsoft is working to resolve an Exchange Online issue causing email access problems for Outlook mobile users who use Hybrid Modern Authentication (HMA).
HMA is a Microsoft Exchange Server feature that allows users to access on-premises mailboxes using authorization tokens from the cloud.
Tracked under EX1137017 in the Microsoft 365 Admin Center, this known issue is caused by a recent service change, designed to improve the efficiency of mailbox syncs, which is triggering 12-hour sync delays for affected customers.
The issue began impacting Outlook mobile users on August 17, causing some mailboxes to crash and preventing affected customers from accessing their email and calendars.
“Some users may be unable to send or receive email from the Outlook mobile app on their devices,” the company says in the service alert.
“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.”
Redmond’s engineers have deployed a fix that addresses these problems by ensuring that the syncs no longer enter the quarantine state, after a previous configuration change that would’ve changed the configured delay interval to one hour wasn’t successful.
While Microsoft has yet to disclose which regions or how many customers are impacted by these ongoing Exchange Online problems, this service issue has been classified as an incident, which typically involves noticeable user impact.
According to another recently added service alert (TM1134507) tagged as limited in scope or impact, the company is also investigating and attempting to resolve an issue affecting Microsoft Teams users, causing them to see blank screens and experience freezes during meetings and calls when using the desktop app.
This issue may potentially affect users on devices with Intel driver 32.0.101.69xx versions. Affected customers are advised to use the Microsoft Teams web app as a temporary workaround until the issue is fixed.
In July, Microsoft also addressed a DNS misconfiguration that was causing one-time passcode (OTP) message delivery failures in Exchange Online for some users. One month earlier, it fixed a known issue that caused the classic Outlook email client to crash when starting a new message or opening emails.
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