We are running Dynamics 365 version 9 and Dynamics 365 for Outlook (the add-on)and the issue is intermittent. A user creates and sends an email out of CRM and it goes out with a tracking token but although the response gets back to the user's Outlook mailbox with the tracking token still on it, it never makes it to CRM, the user has to manually track the email. On Personal options, the user is set to track "Email messages in response to Dynamics 365 Email" and under System settings, we are configured to "Use tracking token"