i have a mailbox that i would like to convert to a share mailbox?

Hello Nolan Naidoo,

an existing user mailbox can be converted into a shared mailbox. The conversion can be completed through either the Microsoft 365 Admin Center or the Exchange Admin Center, provided that you have the appropriate administrator permissions.

In the Microsoft 365 Admin Center, go to: Users > Active users > select the affected user > Mail > Convert to shared mailbox

Alternatively, in the Exchange Admin Center, go to: Recipients > Mailboxes > select the mailbox > More actions > Convert to shared mailbox

The existing emails, calendar items, and Inbox rules are retained during the conversion. After the mailbox has been successfully converted, you can assign Read and manage, Send as, or Send on behalf permissions to the users who need access.

Please keep the following licensing points in mind:

• The mailbox should retain its current Exchange Online license until the conversion has been completed successfully.
• After conversion, the license can generally be removed if the shared mailbox is smaller than 50 GB and does not require licensed features.
• A shared mailbox larger than 50 GB requires an appropriate Exchange Online license, such as Exchange Online Plan 2, to support a mailbox size of up to 100 GB.
• A license may also be required for features such as an online archive, litigation hold, or certain advanced retention capabilities.
• Please do not delete the original user account after the conversion, because the account remains connected to the shared mailbox.
• If the mailbox belonged to a former employee, consider blocking sign-in and resetting the password after the conversion to prevent direct access using the old credentials.

You can find the complete procedures and licensing considerations in the following official Microsoft documentation:

Convert a user mailbox to a shared mailbox | Microsoft 365 admin

Convert a mailbox in Exchange Online | Microsoft Learn

After completing the conversion, please verify that the mailbox appears under Teams & groups > Shared mailboxes in the Microsoft 365 Admin Center, then assign the required members and permissions.

I hope this helps you complete the conversion safely while preserving the existing mailbox data.

Kind regards,

If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment". 

Note: Please follow the steps in documentation to enable e-mail notifications if you want to receive the related email notification for this thread.