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sync quarantine
About this tag
The sync quarantine tag on WindowsForum.com covers issues where mobile or cloud email clients are quarantined due to authentication or sync failures in Exchange Online. A key thread discusses a Microsoft-acknowledged regression (EX1137017) affecting Outlook mobile users with Hybrid Modern Authentication (HMA), where devices were placed in a 12-hour sync quarantine, preventing mail send/receive. The fix is being rolled out by Microsoft. Discussions focus on troubleshooting HMA sync quarantine, understanding the root cause, and applying the official resolution. This tag is relevant for IT administrators managing Exchange Online and hybrid deployments.
Microsoft has acknowledged and begun rolling out a fix for a troubling Exchange Online regression that left some Outlook mobile users unable to send or receive mail — a problem traced to Hybrid Modern Authentication (HMA) and tracked inside the Microsoft 365 Admin Center as incident EX1137017...
admin guidance
change validation
cloud optimization
ex1137017
exchange online
hma
hybrid identity
incident management
incident response
mail delivery delays
microsoft 365
mobile sync
modern authentication
outlook mobile
runbooks
service degradation
service health
syncquarantine
teams tm1134507
telemetry observability