Adaptive Scope Sytntax

Hi.

I have a requirement to scope only "UserMailbox" data in an Adaptive scope to ensure only user mailbox data is retained and deleted > 7years and shared mailbox is not in scope and retained forever. This scope will then be used in Adaptive Exchange Online Retention policy to Retain and then delete email > 7years old. Could anyone help me define the syntax to use in the query please? I have used the following but am not sure if this is correct even though it never failed when I completed the Adaptive Scope

RecipientTypeDetails -eq 'UserMailbox'

Thanks in Advance

Chris