After a couple of month with no issues suddenly Appointments Contacts and Tasks are not synched.
The sync test however succeeds on incoming and outgoing emails.
It turns out that users were migrated to another Exchange.
In Acync logging I see errors while testing like:
Crm Exception: Message: subscriptionclients with clientid fc91beff-d3fa-e311-940f-0050569b2037 doesn't exist, ErrorCode: -2147204845
I asked the Exchange admin to resolve the GUID for the user I tested and retrieved this:
MailboxGuid van User is: ce57b022-30c3-4c2e-8d5b-2c41bf9cec51
So...
How do I fix this issue?
Do I have to rebuild the serverside connection from scratch?