Microsoft working on fix for ongoing Outlook email issues
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 delay