Convert Shared mailbox to regular > The password is invalid. Unable to update the password

This week I had a customer, who wanted to convert a shared mailbox to a regular mailbox, on an Exchange 2016 server.

Normally this must be done by Exchange powershell:

Set-Mailbox username -Type regular

This time there was an error :

Active Directory operation failed on FQDN.domain.local. The password is invalid. Unable to update the password. The value provided for the new password does not meet the length, complexity, of history requirements of the domain.

This means there us something wrong with the password used for this mailbox.

Error message in PowerShell

Solution:

Change the password for the shared mailbox, and try the PowerShell command again, it will now succeed !

The mailbox is now converted to a regular mailbox.