Title: Some users’ encrypted email messages sent from a shared mailbox to external domains may fail to send in Exchange Online
User impact: Users’ encrypted messages sent from a shared mailbox to external domains may have failed to send in Exchange Online.
Final status: We’ve confirmed with a subset of affected users that our additional optimizations were successful at resolving impact, and the issue is remediated for all users.
Scope of impact: This issue impacted some users’ encrypted email messages sent from a shared mailbox to external domains in Exchange Online.
Start time: Tuesday, March 12, 2024, at 6:17 AM UTC
End time: Friday, March 15, 2024, at 11:16 PM UTC
Root cause: A recent change, which was intended to enable the service to perform rule evaluation at the component level, rather than at the email message level, had increased the amount of requests to the service responsible for providing the license to encrypt or decrypt messages, resulting in our traffic management systems to be initialized and failing these requests to the service.
Next steps:
– We’re reviewing our change testing and validation procedures to identify opportunities to improve impact detection and prevent similar future occurrences.
This is the final update for the event.
