When the Change Request reaches Implementing status, all the users who are responsible for a Task will receive an email notification.
Users who have been assigned a Custom Task will receive an email notification indicating that the Change Request has reached Implementing status and that they are being notified because they are configured as a Responsible User for one of the Change Request Tasks.
If Update Document Tasks have been created for the Change Request, the users who have a role in the Documents that are to be updated will also receive an email notification indicating that the Document(s) have been Force Reviewed and are now in Draft status as a consequence of the Change Request.