[Updated] Exchange Online Gets Auto-Archiving Support to Prevent Mailbox Overloads
This new feature ensures uninterrupted email flow and efficient mailbox management.
Key Takeaways:
- Microsoft introduces threshold-based auto-archiving for Exchange Online to prevent mailbox overloads.
- The feature activates automatically when storage nears capacity, ensuring smooth email flow.
- It works alongside existing archiving policies without altering retention or deletion settings.
Microsoft has introduced a new auto-archiving feature for Exchange Online customers. The latest update brings smart, threshold-based archiving that automatically manages mailbox storage before it reaches capacity.
What is the problem with traditional time-based archiving?
A key drawback of relying solely on time-based archiving in Exchange Online is that it only moves emails to the archive after a specific period, such as two years, regardless of how quickly a mailbox fills up. In today’s environment, where users frequently receive large attachments, automated messages, and AI-generated content, mailboxes can reach their storage limits much faster than the archiving schedule anticipates. This delay in archiving can lead to users hitting quota limits, which disrupts email flow and requires manual intervention.
How does auto-archiving work?
Auto-archiving in Exchange Online works by automatically moving older emails to the archive mailbox when the primary mailbox reaches 90% of its storage capacity. This feature monitors mailbox usage and responds dynamically to prevent quota limits from being exceeded. It identifies the oldest items based on their received date and transfers them to the archive until the mailbox usage drops below the threshold.
“The Managed Folder Assistant will continuously monitor the primary mailbox size. As and when primary mailbox size exceeds 90% of the current mailbox quota and provided the archive mailbox is provisioned and has remaining space, Managed Folder Assistant will automatically archive the oldest items first until usage drops below the threshold. The same concept applies to Recoverable Items (“Dumpster”) folders when they near their quota. SLA of running Managed Folder Assistant on a given mailbox is 7 days,” the Exchange team explained.
How does auto-archiving integrate with existing policies?
Auto-archiving in Exchange Online is designed to work seamlessly without interfering with existing mailbox policies. It respects the “Never Move to Archive” tags and does not change deletion or retention policies. Auto-archiving still activates to manage storage even if a mailbox is under Retention Hold.
However, this feature does not provision archive mailboxes or enable auto-expanding archives. It can’t be disabled because it is a failsafe mechanism to prevent any mail flow disruption.
Microsoft is currently rolling out auto-archiving for Exchange Online to commercial customers worldwide, with government cloud customers to follow in November 2025. Admins can use Export-MailboxDiagnosticLogs via Exchange Online PowerShell to audit Auto-Archiving activity.
[Update] 10/9/2025 6:09 AM PT: Microsoft has since decided to delay the rollout of this auto-archiving feature due to massive backlash from IT administrators. “We heard your feedback and are working on revised release plan for this feature. We will update this post (and release plan) accordingly in the near future,” Microsoft wrote in an update to the original blog post.
Rabia has a master's degree in Software Engineering and she has years of experience writing professionally about Microsoft products and other technologies. Rabia has also written for OnMSFT.com as well as Windows Report. She is always up to date on t...
