Configuring Microsoft 365 Archiving Policy

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Each mail-enabled Microsoft 365 user with the correct license can use the Online Archive (formerly referred to as In-Place Archive in legacy Exchange documentation) mailbox feature. An Online Archive is a special type of mailbox associated with a user’s mailbox and is available in both Outlook and Outlook on the web.

Users can use the archive mailboxes along with their primary mailboxes. If your mailbox has become too large and you cannot receive or send emails, you can configure automatic archiving in an Online Archive.

Key Behavior and Limitations

Archive Policies in Microsoft 365 allow you to define rules for when your email items will automatically move from your mailbox to the Online archive. By default, archive mailbox data requires an Internet connection. In cached Exchange mode, items from the archive are not downloaded locally (unless configured).

Also, when searching in a mailbox, archive mailbox items may not always appear in search results by default (depending on the Outlook version, search scope, and cache settings).

Exchange Online Archive Eligibility

Not all Exchange mailboxes are eligible for online mailbox archiving. The eligibility and maximum archive mailbox size depend on your license.

• With Microsoft 365 Business Basic, Standard, and E1 base licenses, the archive mailbox size is limited to 50 GB;
• Auto-expanding archiving is available with eligible Exchange Online Archiving licenses. It can automatically expand the archive mailbox from the initial 100 GB up to 1.5 TB.
  You can enable it using command:
  Enable-Mailbox -Identity user@domain.com -AutoExpandingArchive

Enabling Exchange Online Archive Mailbox

By default, Online Archive is not enabled for all Microsoft 365 users, even those with the appropriate license. You can turn the online archive on or off through the Exchange Admin Center or Exchange Online PowerShell.

Using the Exchange Admin Center to Enable Archive Mailbox

1. Log in to the Exchange Admin center.
2. Navigate to Recipients > Mailboxes and click the mailbox to manage.
3. Click the Others tab and Manage mailbox archive.
   

   

4. Here you can turn Exchange Online Archiving on or off. The Name field is optional.
   

   

   Once enabled, you’ll see the archive mailbox statistics on this page. If you did not customize the archive mailbox name, Exchange may use the “In-Place Archive –” naming convention for the archive mailbox.
   

   

Using the Exchange Online PowerShell to Enable Archive Mailbox

You can also enable Online Archive using PowerShell:

1. Connect to Exchange Online PowerShell:
   

   Connect-ExchangeOnline

   Note. Keep in mind that Exchange Online PowerShell requires the ExchangeOnlineManagement module and supports Modern Authentication (MFA). Legacy authentication is not supported!
   
2. Run the below command to enable the Exchange Online archive mailbox for the specified user.
   

   Important note. Before enabling the archive, you need to ensure that you assigned the appropriate license for the users. Without a valid license, the storage will be limited to 50 GB.

   Enable-Mailbox -Identity fotis.albert -Archive

   
3. Once Online Archive is enabled, run this command to verify the archive name:
   

   Get-Mailbox -Identity fotis.albert | Select-Object ArchiveName,ArchiveGUID

   
4. A separate ”Online Archive – User” mailbox will appear in the Outlook client and Outlook Web App.
   

   Note that in Outlook, the archive mailbox appears as a separate mailbox. Of course, as a user you browse it like a regular mailbox, but keep in mind that items are stored in Exchange Online and are not cached locally by default in Outlook cached mode (depending on sync settings).

   

You can enable archive mailboxes for all licensed users at once:

Get-Mailbox -RecipientTypeDetails UserMailbox -ResultSize Unlimited |
Where-Object {$_.ArchiveStatus -eq "None"} |
Enable-Mailbox -Archive

Hint. Note that the Archive folder inside a mailbox is not the same as the Online Archive mailbox! The Archive folder is a standard mailbox folder, while Online Archive is a separate mailbox database stored in Exchange Online.

How to Use Archive Mailbox

Users can manually move items from the primary mailbox to the Online Archive. In Outlook, select an email, right-click it, and choose Move > Online Archive.

How to Assign Archive Policy

They can also apply archiving policies for a more streamlined and automated approach.

Four archiving policies that can be applied to mailbox folders are available. Select the folder to which you want to apply the archive policy to, right-click on it, and select the Archive Policy you need:

• Personal 1 year move to archive
• Personal 5 years move to archive
• Personal never move to archive
• Use parent folder policy
  

  

Note. Folder-level “Archive Policy” in Outlook is a client representation of Exchange MRM retention tags applied server-side.

Creating a New Microsoft 365 Archiving Policy

Important. Note that our article focuses on Exchange Online MRM (Messaging Records Management) archive policies that move items to the Online Archive mailbox. These policies are different from Microsoft Purview Retention Policies and Retention Labels (which are used for compliance, records management, and data lifecycle governance across Microsoft 365 workloads).

The out-of-the-box archive policies are few and insufficient for some organizations. But an Exchange Online administrator can create additional archiving policies for Outlook using the Microsoft 365 Admin Center or using PowerShell.

Suppose you want to create a new archiving policy that automatically moves items to the user’s Exchange Online Archive mailbox.

Here’s the process using PowerShell:

In the example below, we use -Type All to create a Default Policy Tag (DPT) that automatically applies the 90-day archive rule to eligible mailbox items. Unlike Personal tags, which users can manually assign to individual folders, a DPT is applied automatically through the MRM retention policy. Run the following command to create a new archiving policy that automatically moves eligible items older than three months to the Online Archive:

New-RetentionPolicyTag "Default 3 Month Move to Archive" -Type All -RetentionEnabled $true -AgeLimitForRetention 90 -RetentionAction MoveToArchive

This command creates a new default retention policy tag named “Default 3 Month Move to Archive” that moves eligible items older than 90 days to the Online Archive.

Now that the retention tag has been created, we must include it in a new or existing MRM retention policy. In this example, we’ll add the newly created ‘Default 3 Month Move to Archive’ retention tag to the ‘Default MRM Policy’ retention policy.

$retentionPolicy = "Default MRM Policy"
$policyTag = "Default 3 Month Move to Archive"

# Get policy (fail fast)
$policy = Get-RetentionPolicy $retentionPolicy -ErrorAction Stop

$taglinks = $policy.RetentionPolicyTagLinks

# Safety normalization
if (-not $taglinks) {
$taglinks = @()
}

# Prevent duplicates
if ($taglinks -notcontains $policyTag) {
$taglinks += $policyTag
}

# Apply once
Set-RetentionPolicy -Identity $retentionPolicy -RetentionPolicyTagLinks $taglinks

Note. You must assign Retention policies to mailboxes. The Default MRM Policy is used as a tenant-wide default only when no custom policy is assigned.

The Managed Folder Assistant runs on a background schedule and processes mailboxes asynchronously. Policy application may take from several hours up to 24 hours (depending on mailbox size and service load). Once processed, users will see the updated archiving behavior in Outlook and can apply it to folders and items.

Hint. In Microsoft 365, you can also configure Microsoft 365 retention policy which defines when an email will be deleted.

Conclusion

Configuring a Microsoft 365 archiving policy is crucial for effective data management and compliance. This blog post explored the steps involved in setting it up.

By understanding retention tags, policies, and actions, organizations can customize their archiving policies to meet their specific needs.

Regular monitoring and user education are essential for maintaining policy effectiveness. A well-configured archiving policy ultimately promotes responsible data management, regulatory compliance, and improved data governance.