Auto Archiving for Exchange Online automatically moves oldest mailbox items to archive when usage exceeds 96%, preventing mail flow disruption. Enabled by default, it applies to mailboxes with archives, respects "Never Move to Archive" tags, and allows admin adjustments or disabling. Rollout starts January 2026.
Applies to: Microsoft Purview
Source: mc.merill.net — data via Merill Fernando's open archive (MIT).