TL; DR: Auto-Archiving for Exchange Online is being rolled out in October 2025 for all public clouds and in November for all government clouds. If archiving is already enabled for Exchange Online use...
Published Oct 07, 2025
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I’m curious, what’s new about this rollout? It seems that auto-archiving already exists in public clouds.
Also, what happens if auto-archiving isn’t enabled for a user’s Exchange Online account? Based on my experience, the emails remain stored in the primary mailbox. However, if auto-archiving is enabled, older emails are automatically moved to the archive mailbox when the primary mailbox reaches around 90% of its storage quota.
Karthik_MSMicrosoft
Items from the primary mailbox are moved to the archive mailbox based on the configured archiving policy. For example, if a user’s mailbox has a “5-year move to archive” policy but reaches capacity within 2 years, it may impact the user's ability to send or receive emails.
If the archive mailbox is enabled for the user, this feature will override the standard archiving policy and begin archiving items proactively once the mailbox reaches a critical threshold. This helps prevent any disruption to mail flow.
However, if the archive mailbox is not enabled, the system will not provision one automatically, and the current configuration will remain unchanged.