Exchange Online Backup Failures (Forbidden Errors)

Incident Report for m2

Identified

We are tracking reports of "Forbidden" errors during Office 365 backups caused by a recent Microsoft Exchange Online behavior change. This affects specific tenants and mailboxes using EWS.

Exchange Online jobs may show User Mailboxes reporting a Mailbox Status of:
Throttling from Exchange, Failed to process mailbox due to [The request failed. Forbidden]

Resolution:
Additional information and steps to resolve this can be found here, https://support.commvault.com/Article/Details/KA-191556

Posted Apr 01, 2026 - 16:50 UTC

This incident affects: Office 365 (Australia East, East US2, UK South, Canada Central).