Complete Setup Guide: How to Enable and Manage Online Archiving in Exchange Online

As organizations grow, so does the volume of email data. Managing this data effectively is critical for compliance, security, and performance. Microsoft Exchange Online offers a powerful feature called online archiving, also known as In-Place Archiving, which provides users with additional mailbox storage and supports long-term retention strategies.

This guide walks you through the complete setup of online archiving in Exchange Online—from prerequisites to enabling and managing archive mailboxes, including auto-expanding archiving.

What Is Online Archiving in Exchange Online?

Online archiving is a cloud-based mailbox storage solution that allows users to store older emails in a separate archive mailbox. This helps reduce the size of the primary mailbox while ensuring older messages remain accessible and compliant with retention policies.

Licensing and Requirements

To use online archiving, users must be licensed appropriately. The feature is included by default in the following Microsoft plans:

✅ Plans That Include Online Archiving:

• Exchange Online Plan 2

• Microsoft 365 Business Premium

• Microsoft 365 E3

• Microsoft 365 E5

• Microsoft 365 F5 Compliance

• Office 365 E3

• Office 365 E5

• Office 365 A3

• Office 365 A5

🛠️ Plans That Require Online Archiving as an Add-On:

• Exchange Online Plan 1

• Exchange Online Kiosk

• Microsoft 365 Business Basic

• Microsoft 365 Business Standard

• Office 365 E1

• Office 365 A1

• Office 365 G1

• Office 365 F3

• Microsoft 365 F3

Each archive mailbox is tied to a single user and cannot be used for shared or journaling purposes.

How to Enable Online Archiving

You can enable archive mailboxes via the Exchange Admin Center (EAC) or PowerShell.

Using Exchange Admin Center (EAC):

1. Sign in to EAC.

2. Go to Recipients > Mailboxes.

3. Select a user and click Others > Manage mailbox archive.

4. Toggle Mailbox archive to On, then click Save.

5. The archive mailbox will appear as "Active" in the Archive status column.

Using PowerShell:

The first step is to connect to Exchange Online PowerShell. For instructions, see Connect to Exchange Online PowerShell.

To enable for a single user:

Enable-Mailbox -Identity <username> -Archive

To enable for all users without an archive:

Get-Mailbox -Filter {ArchiveGuid -Eq "00000000-0000-0000-0000-000000000000" -AND DisabledArchiveGuid -Eq "00000000-0000-0000-0000-000000000000" -AND RecipientTypeDetails -Eq "UserMailbox"} | Enable-Mailbox -Archive

Auto-Expanding Archiving

When a user's archive mailbox reaches 90 GB, Exchange Online can automatically expand it — up to 1.5 TB.

Enable for Entire Organization:

Set-OrganizationConfig -AutoExpandingArchive

Enable for Specific Users:

Enable-Mailbox  -AutoExpandingArchive

Important Notes:

• Auto-expanding archiving cannot be disabled once enabled.

• It may take up to 30 days for additional storage to be provisioned.

• Only supported for cloud-based archive mailboxes.

Retention and Compliance

Exchange Online uses Messaging Records Management (MRM) to manage email lifecycle. By default, Exchange Online applies a retention policy that moves items older than 2 years to the archive mailbox.

MRM uses retention tags to define how long items are kept and what happens when they reach their retention age. These tags are grouped into retention policies, which are then assigned to mailboxes.

There are three types of retention tags:

• Default Policy Tag (DPT): Applies to all untagged items in a mailbox.

• Retention Policy Tag (RPT): Applies to default folders like Inbox or Deleted Items.

• Personal Tag: Users can apply these to custom folders or individual items.

For example, you can create a policy that:

• Moves items older than 3 years to the archive mailbox.

• Deletes items in the Deleted Items folder after 1 year.

Steps to Configure Retention Tags and Policies:

1. Create Retention Tags. Microsoft Purview portal > Solutions > Data Lifecycle Management > Exchange > MRM Retention tags.

2. Create a Retention Policy. Microsoft Purview portal > Solutions > Data Lifecycle Management > Exchange > MRM Retention policies.

3. Assign the Policy to Mailboxes. Microsoft Exchange admin portal > Recipients > Mailboxes > Select the mailbox > Manage mailbox policies > Retention policy > Select your policy.

4. Run the Managed Folder Assistant:

Start-ManagedFolderAssistant -Identity user@domain.com

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