You must be a Global, License, or User admin to continue with the assign/unassign of licenses. You will need to be an Exchange admin to convert a regular or shared mailbox.
BEFORE YOU MOVE ON
Do not remove a user’s license before converting their mailbox to shared, or you will need to add the license back before proceeding.
Advantages of converting a user’s mailbox to a Shared Mailbox
As a best practice, organizations should review their Active Users regularly. If a user is inactive in your organization, chances are they aren’t checking their email anymore; a shared mailbox ensures others will see emails that may come to that user’s inbox from customers, clients, vendors, etc. Don’t miss out on important emails because of an inactive mailbox!
Revoking unused licenses can help cut costs and ensure you have enough licenses available for active users. This is especially true for nonprofits that pay on a per-license basis on limited funding.
You do not need to delete the user’s account when they become inactive or leave your organization, however, as removing the license will remove any associated costs and prevent them from further sign-in until a license is reassigned.
Converting from a regular mailbox to a shared mailbox
To convert from a regular mailbox to a shared mailbox, navigate to Exchange admin center > Mailboxes and select the (licensed) user you’d like to convert the mailbox for. If the user is unlicensed, you must assign them a license before continuing.
Next, select “Convert to shared mailbox”, “continue”, and let the wizard run until it it confirms the mailbox has been converted successfully.
Converting from a Shared Mailbox to a regular user mailbox
If you chose not to delete the user, you can reassign a license at any time and convert the shared mailbox into a regular mailbox. If you did delete the user, jump down to the resources section for further instructions.
To convert a shared mailbox to a regular mailbox, navigate to Exchange admin center > Mailboxes and select the (licensed) user you’d like to convert the mailbox for.
Next, select “Convert to regular mailbox”, “continue”, and let the wizard run until it confirms the mailbox has been converted successfully. You may want to give it a few minutes for changes to sync across services, so hold off on sending any emails right away.