If you delete the Mailbox from Exchange, it will delete AD account associated with it. So administrators will get very often confused.

So we need to Run Disable-Mailbox to remove mailbox and Exchange properties which will not delete the AD Account.

To remove the mailbox

Run Disable-Mailbox -identity <Mailbox ID>

if you run, Get-Mailbox -Identity Administrator, You will get an Below Error as there is no Mailbox Associated with it

Now you will create another mailbox for the same user without any issues,

Open Exchange admin center–>Recipients–> Mailboxes–> Click on User Mailbox

Click on Browse

Select Administrator(Ad User)

Click on More Options

Select the Mailbox Database 

So we have seen how to disable mailbox and recreate the mailbox for the same AD User.