I have found that tasks do not synchronize between Dynamics 365 and Outlook. Now I wonder what the right setting is to get this done.
The 'Appointments, Contacts and tasks' I originally had on server synchronization. This synchronization did not work. Now that I have put it on 'Microsoft Dynamics 365 for Outlook' this synchronization does work, but Dynamics indicates the following under 'Mailboxes' under 'Status of appointments, contacts and tasks': 'Not executed'.