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Can a Shared Mailbox Keep a 300 GB Online Archive in Exchange?
Question details
The user wants to know if a user mailbox containing 40 GB of primary data and a 300 GB online archive can be safely converted to a shared mailbox without encountering storage quota issues.
- Product
- Microsoft Exchange Online
- Device & OS
- not provided
- Scenario
- Converting a heavily utilized user mailbox to a shared mailbox while retaining its large online archive.
- Observed behavior
- The primary mailbox holds 40 GB and the online archive holds 300 GB. The user needs to prevent the newly converted shared mailbox from reaching maximum capacity and blocking new emails.
Before converting the mailbox, check your Microsoft 365 administrative center to verify your available Exchange Online licenses and review the current mailbox storage usage.
Assign an Exchange Online License to the Shared Mailbox
Unlicensed shared mailboxes are limited to a 50 GB quota. To retain a 300 GB online archive, you must assign a qualifying license to expand the storage capacity.
By default, converting a mailbox to a shared mailbox removes the need for a license, but caps the total storage (including archives) at 50 GB. Since your online archive alone is 300 GB, leaving it unlicensed will cause the mailbox to instantly become full, preventing it from sending or receiving new emails.
To support a 300 GB archive, you must assign an Exchange Online Plan 2 license, which increases the primary mailbox size to 100 GB and enables auto-expanding archiving.
Log in to the Microsoft 365 admin center using your global or Exchange administrator credentials.
Navigate to the 'Users' menu on the left pane, click on 'Active users', and search for the specific shared mailbox.
Select the mailbox, go to the 'Licenses and apps' tab, and check the box for 'Exchange Online Plan 2' (or Plan 1 with an Exchange Online Archiving add-on).
Click 'Save changes'. Once applied, the mailbox quota will be updated, safely accommodating your 40 GB primary data and 300 GB online archive.
Reduce Mailbox Size via Local PST Export
If you do not want to purchase an additional license, you must reduce the combined mailbox and archive size below the 50 GB free shared mailbox limit.
Manage Your Daily Workflow Seamlessly with WPS Office
While Microsoft Exchange handles complex mailbox configurations and large online archives, you need a reliable suite for your local documents. WPS Office provides a lightweight, budget-friendly alternative that integrates smoothly with your daily workflow.
- 1. Download the Installer: Visit the official WPS Office website and download the free installation package for your operating system.
- 2. Install the Suite: Run the downloaded executable file and follow the quick on-screen instructions to install the software.
- 3. Open and Edit Files: Launch WPS Office to instantly start creating, opening, or editing your Microsoft Office compatible documents.
Frequently Asked Questions
What is the maximum storage limit for a free shared mailbox?
By default, an unlicensed shared mailbox in Microsoft 365 has a maximum storage quota of 50 GB. If your mailbox data (including the archive) exceeds this, you must either delete data or assign an appropriate Exchange Online license to increase the limit.
Can I enable auto-expanding archiving on a shared mailbox?
Yes, provided the shared mailbox is assigned an Exchange Online Plan 2 license. Once appropriately licensed, you can turn on auto-expanding archiving via the Exchange admin center or PowerShell to accommodate massive archives.
Will I lose my archive data if I convert an oversized mailbox without assigning a license?
You will not instantly lose the existing data during the conversion process. However, because the data exceeds the 50 GB free threshold, the mailbox will immediately become full and be restricted from receiving or sending any new emails until a license is applied or space is cleared.
