Compliance Problems

How to Fix Exchange Retention Policy Not Purging Deleted Mailbox Items

Adam Davis Oct 10, 2026 869 views

Question details

The user needs to resolve an issue where an MRM retention policy fails to permanently remove items older than 1,095 days from users' Deleted Items folders.

Fixing Exchange Retention Policy Not Purging Deleted Mailbox Items

Product: Microsoft Exchange
Device & OS: not provided
Scenario: Managing mailbox storage and compliance using an MRM retention policy to automatically clear old deleted emails.
Observed behavior: The configured MRM retention policy does not purge items that are already three years old from the Deleted Items folder.

Before you start

Ensure you have Exchange Administrator or Compliance Administrator permissions in Microsoft 365 and have the Exchange Online PowerShell module installed to verify policy settings.

Solution 1Recommended

Verify Policy Settings and Run the Managed Folder Assistant

Check if the correct retention tag is applied to the policy and manually trigger the folder assistant to force immediate processing.

Retention processing in Microsoft Exchange is not immediate. It operates on a background cycle known as the Managed Folder Assistant, which typically processes mailboxes once every few days. You can manually force this assistant to run via PowerShell.

Verify the Retention Tag

Navigate to the Exchange admin center, go to Compliance Management > Retention tags, and ensure your tag specifically targets the 'Deleted Items' folder with the action set to 'Permanently Delete' after 1,095 days.

Confirm Policy Assignment

Check the mailbox properties of the affected users to ensure the correct MRM retention policy (containing your newly created retention tag) is actually assigned to their mailboxes.

Force the Managed Folder Assistant

Open Exchange Online PowerShell and run the command: Start-ManagedFolderAssistant -Identity <UserEmailAddress>. This forces the assistant to process the specific mailbox.

Allow Time for Processing

Wait for 24 to 48 hours. Depending on the size of the mailbox and server load, the purge process can take significant time to complete.

Verify Policy Settings and Run the Managed Folder Assistant

Processing Delays: Even after forcing the Managed Folder Assistant, it may take several days for items to fully purge if the mailbox contains a massive volume of emails.

Solution 2

Check for Conflicting Compliance Holds

Ensure that overriding compliance settings, such as Litigation Holds or Delay Holds, are not preventing the deletion of old items.

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Frequently Asked Questions

Why is the Managed Folder Assistant not deleting emails immediately?

The Managed Folder Assistant runs on a background schedule and processes mailboxes periodically (typically once every 7 days). Even when triggered manually via PowerShell, it might take hours or days to fully process a large mailbox and remove the items.

Can a Litigation Hold override an MRM retention policy?

Yes. If a mailbox is placed on Litigation Hold or an eDiscovery Hold, items will be preserved for discovery purposes. Even if an MRM policy attempts to permanently delete them from the Deleted Items folder, they will be kept in the Recoverable Items folder until the hold expires.

How do I know which retention policy is currently applied to a specific mailbox?

You can check this in the Exchange admin center by opening the mailbox properties, navigating to the Mailbox features tab, and viewing the assigned Retention Policy. Alternatively, you can use the Get-Mailbox PowerShell cmdlet to view the applied policy.

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