Exchange Online Mailbox Retention Policy (MRM) Management Guide

Office/Azure/Exchange
📅 January 21, 2026 ⏱️ 5 min read ✍️ Andy
#Exchange #Office365 #PowerShell #MRM

1. Check Mailbox Retention Policy Configuration

View current retention policy assigned to mailbox

Get-Mailbox "user" | Select-Object RetentionPolicy

Check if MRM processing is enabled

Get-Mailbox "user" | Select ElcProcessingDisabled
  • Returns False = Enabled (normal)
  • Returns True = Disabled (needs to be enabled)

Check mailbox archive status

Get-Mailbox "user" | Select ArchiveStatus,ArchiveName
  • ArchiveStatus: Active = Archive enabled
  • ArchiveStatus: None = Archive needs to be enabled

2. Configure Retention Policy and Archive

Assign retention policy to mailbox

Set-Mailbox "user" -RetentionPolicy "PolicyName"

Enable mailbox archive

Enable-Mailbox "user" -Archive

3. View Retention Policy Details

View retention tags linked to policy

Get-RetentionPolicy "PolicyName" | Select Name,RetentionPolicyTagLinks

View detailed retention tag rules (Important)

Get-RetentionPolicy "PolicyName" | Select -ExpandProperty RetentionPolicyTagLinks | ForEach-Object {Get-RetentionPolicyTag $_ | Select Name,Type,AgeLimitForRetention,RetentionAction,RetentionEnabled}

Key Field Explanations:

  • AgeLimitForRetention: Retention period (e.g., 365.00:00:00 = 365 days ≈ 1 year)
  • RetentionAction: Action type (MoveToArchive = Move to archive, DeleteAndAllowRecovery = Delete)
  • Type: Scope (All = All items)

4. Manually Trigger MRM Processing (Very Important)

Immediately trigger Managed Folder Assistant

Start-ManagedFolderAssistant "user"

Notes:

  • Exchange Online automatically runs MRM every 7 days by default
  • This command triggers processing immediately without waiting
  • Wait 15-60 minutes after execution to see results

5. Verify MRM Running Status

Check MRM last run time (may not be accurate)

Get-MailboxStatistics "user" | Select DisplayName,ElcLastRunTime,ElcLastSuccessTimeStamp

Note: The ElcLastRunTime field may not update in Exchange Online even when MRM is running normally

Check archive mailbox content (Most reliable verification method)

Get-MailboxStatistics "user" -Archive | Select ItemCount,TotalItemSize

This is the best way to verify MRM is working:

  • Run this command periodically
  • If ItemCount and TotalItemSize increase, items are being archived
  • More reliable than ElcLastRunTime

Check primary mailbox statistics

Get-MailboxStatistics "user" | Select ItemCount,TotalItemSize,LastLogonTime

Troubleshooting Workflow

Issue: MRM appears not to be running

  1. Check if retention policy is assigned
  2. Verify ElcProcessingDisabled is False
  3. Check if archive mailbox is enabled
  4. Manually trigger Start-ManagedFolderAssistant
  5. Wait 30-60 minutes and check archive mailbox item count

Issue: ElcLastRunTime remains empty

  • This is normal behavior and doesn’t mean MRM isn’t running
  • Use Get-MailboxStatistics -Archive to verify by checking archive growth

Issue: No items being archived

  • Check the retention policy’s AgeLimitForRetention (retention days)
  • Confirm primary mailbox contains items older than the age limit
  • Use Get-MailboxFolderStatistics -IncludeOldestAndNewestItems to view oldest item dates

Best Practices

  1. Monitor archive growth regularly instead of relying on ElcLastRunTime
  2. Manually trigger immediately after assigning new policy using Start-ManagedFolderAssistant
  3. Regularly check archive mailbox capacity to avoid quota exceeded
  4. Document retention policy rules to ensure compliance requirements are met