Recently when a user was trying to use set regarding for a tracked email they were receiving the following error.
'You do not have enough privileges to acces the Micrsoft Dynamics CRM object or perform the requested opeartion.'
When running the CRM trace we found this error 'SecLib::AccessCheckEx failed. Returned hr = -2147187962, ObjectID: b043cc71-a644-e611-80d7-005056a076e4, OwnerId: 9d589563-f988-dd11-8b66-0013211ccf00, OwnerIdType: 8 and CallingUser: e2619700-963c-e111-9119-005056932219. ObjectTypeCode: 4200, objectBusinessUnitId: c7ec9cc6-9e67-db11-97e6-0013211cbfff, AccessRights: WriteAccess'
It turns out CRM 2016 sets the owner automatically based off who sent the email rather than who created the tracked record. We had a disabled user in MSCRM in a different business unit that when ever another user tried to track an email from them it would set the disabled user as the owner! Reassigning the email fixed the issue and I found a few more that were problematic using advanced find.