Microsoft is investigating a widespread service issue causing authentication issues and email delays and failures for Exchange Online customers.
It first acknowledged this incident (tracked under EX1464935 in the admin center) at 5:30 PM UTC, when it began investigating a stream of reports from users on social media.
According to outage tracking service Downdetector, tens of thousands of Exchange Online users are affected and experiencing issues receiving emails via Outlook and accessing the Exchange Online platform.
Microsoft says the list of symptoms includes:
Delays or failures when sending or receiving email messages.
