An archive mailbox gives users a separate location for storing older email without filling their primary mailbox. However, the standard archive can eventually reach its storage limit, especially for users who must retain years of email. Auto-expanding archiving helps address this by automatically adding storage space to an Exchange Online archive as it fills. Once enabled, the archive can grow beyond its initial 100 GB capacity, up to a maximum of 1.5 TB. This guide explains the requirements and important limitations of auto-expanding archiving, along with the methods for enabling it.
What Is Auto-Expanding Archiving?
Auto-expanding archiving is an Exchange Online feature that adds storage to an archive mailbox when more space is required. When the archive, including its Recoverable Items folder, reaches 90 GB, Exchange Online begins provisioning additional archive storage. The extra storage does not appear as one large mailbox.
Exchange Online adds auxiliary archive mailboxes in the background and presents them to the user as part of the same online archive. This process is automatic, and administrators cannot manually change the auto-expanding archive quota. Provisioning additional storage can take up to 30 days. Therefore, it is better to enable the feature before an archive mailbox is completely full.
Prerequisites to Enable Auto-Expanding Archiving
Before enabling auto-expanding archiving, confirm the following requirements:
Supported license: The mailbox must be assigned an Exchange Online Plan 2 license, a standalone Exchange Online Archiving add-on, or a Microsoft 365 license that includes the required archiving entitlement.
Active archive mailbox: The user’s archive mailbox must already be enabled.
Required permissions: To enable the feature for the entire organization, you must be a Global Administrator or a member of the Organization Management role group. To enable it for an individual mailbox, you must belong to a role group that includes the Mail Recipients role.
Important: Auto-expanding archiving is not intended as a general-purpose repository for messages belonging to multiple users. Microsoft supports it for individual user mailboxes and eligible shared mailboxes with an archive growth rate that does not exceed 1 GB per day.
Enable the User’s Archive Mailbox in Exchange Online
Auto-expanding archiving works only when the mailbox already has an online archive. If the archive is not enabled, you can enable it from the Exchange admin center.
- Sign in to the Exchange admin center.
- Go to Recipients > Mailboxes.
- Select the required user.
- Open the Others tab.
- Under Mailbox archive, select Manage mailbox archive.
- Turn on Mailbox archive, and then select Save.
Enabling the archive mailbox and enabling auto-expanding archiving are two separate actions. The archive must be available before you proceed with either of the following methods.
How to Enable Auto-Expanding Archiving in Microsoft 365
Microsoft does not currently provide an option in the Exchange admin center or Microsoft Purview portal to turn on auto-expanding archiving. Administrators can enable it natively through Exchange Online PowerShell.
Method 1: Enable Auto-Expanding Archiving Using PowerShell
Exchange Online PowerShell allows you to enable auto-expanding archiving for a specific mailbox or across the entire organization.
Firstly, connect to Exchange Online PowerShell. If the Exchange Online PowerShell module is not installed, run the following.
Install-Module ExchangeOnlineManagement
Connect-ExchangeOnline To enable auto-expanding archiving for a specific user, run the following by replacing the sample address with the user’s email address.
Enable-Mailbox -Identity "user@contoso.com" -AutoExpandingArchive This approach is useful when only selected users need more archive capacity. For example, it can be enabled for users in legal, finance, or management roles who retain a large volume of email.
If the mailbox is on hold or assigned a retention policy, Microsoft also temporarily increases the primary archive quota and the Recoverable Items quota by 10 GB. This extra capacity helps reduce storage pressure while the additional archive storage is being provisioned.
To enable the feature for all existing and future mailboxes in the tenant, run the below.
Set-OrganizationConfig -AutoExpandingArchive This setting makes auto-expanding archiving available organization-wide. However, each user must still have their main archive mailbox enabled before Exchange Online can add extra archive storage.
Enabling the organization-wide setting does not immediately allocate 1.5 TB to every mailbox. Additional storage is provisioned only when an enabled archive approaches the applicable threshold.
To verify auto-expanding archiving for a user, run the following command.
Get-Mailbox -Identity "user@contoso.com" |
Format-List DisplayName,ArchiveStatus,AutoExpandingArchiveEnabled The output should show:
- ArchiveStatus as Active
- AutoExpandingArchiveEnabled as True
To verify the organization-wide configuration, execute the following command.
Get-OrganizationConfig | Format-List AutoExpandingArchiveEnabled A value of True confirms that auto-expanding archiving is enabled for the organization.
Note: When the feature is enabled through Set-OrganizationConfig, the AutoExpandingArchiveEnabled property on individual mailboxes might not change to True. Check the organization setting to confirm a tenant-wide configuration.
Method 2: Enable Auto-Expanding Archiving Using EasyEntra
The native approach requires administrators to install the Exchange Online PowerShell module, connect to the service, run the correct command, and verify the result. EasyEntra provides a simpler graphical option for enabling the feature on an individual user.
To enable auto-expanding archiving in EasyEntra:
- Open User properties for the required user.
- Select the Mailbox > Mailbox storage tab.
- Click Mailbox Archive and select Enable auto-expanding archiving.
- Review the confirmation message, and then click Enable.
- Click OK twice to apply the changes.
EasyEntra performs the required mailbox action without requiring the administrator to establish a separate PowerShell session or enter the command manually. This is particularly useful when an administrator needs to review a user’s mailbox settings and enable the feature from the same interface!
Limitations of Auto-Expanding Archiving in Exchange Online
The change is permanent: Auto-expanding archiving cannot be turned off after it has been enabled for the organization or an individual mailbox.
Additional storage is not immediate: It can take up to 30 days for Exchange Online to provision more archive capacity.
The 1.5 TB figure is a maximum: Enabling the feature does not immediately assign 1.5 TB. Storage is added gradually as the archive grows.
Archive quotas cannot be customized: Administrators cannot manually change the quota for an auto-expanding archive.
Inactive mailbox recovery is affected: An inactive mailbox with auto-expanding archiving cannot be recovered or restored in the usual way. Its data must instead be exported through Microsoft Purview eDiscovery content search and imported into another mailbox when appropriate.
