1. An email was sent from the "DEAL 999" screen to its respective customer from the CRM, using CRM's exclusive mailbox: backend@domain. 2. The message ID was automatically added in the message body by the CRM. 2. Customer replies to the address (backend@domain) in use only by the CRM. 3. The email is NOT appended to the "Deal 999" Activity log. We have followed this step-by-step, but no success. What happened??? The mailbox backend@domain was once configured as being from a personal mailbox for an employee, but this setting was changed. Could this be interfering?