Outlook 2016 cannot connect to Exchange 2010 PF / Outlook 2010 can

Hello to all,

we have an Exchange 2010/2016 mixed environment and are facing the issue that Outlook 2016 cannot acces PF on an Exchange 2010 CU14 with the users mailbox on an Exchange 2016 CU9. Strangely enough Outlook 2010 with the same user account can and works fine.

Can you help me on that?

Is it required to have a CAS Role is installed on the MDB server?

Thanks