A link is maintained between the information in Outlook and the information in Dynamics 365 (online) to ensure that the information remains current between the two.
Outlook Sync downloads only the relevant Dynamics 365 record IDs to use when a user attempts to track and set regarding an Outlook item. An administrator determines whether your organization’s users are permitted to sync Dynamics 365 data to Outlook by using security roles.
If you use Dynamics 365 for Outlook to track email, the email thread will be visible to users in your organization who have permission to view it.
For every email you receive, Dynamics 365 for Outlook will send Dynamics 365 (online) the sender’s email address, the recipient’s email address, and the subject line of the message.
This change means that Office will never be considered complete.