What can I do if my customer's email reply doesn't appear in the activity stream?

Customer replies to emails sent from Oracle Sales are captured and visible in the application’s UI, under the activity stream for the relevant record. If a customer informs you they replied but you don’t see it in the activity stream, ensure that the original email was sent using the Send Email smart action (not from outside the Oracle Sales application) and that your outbound email configuration is correct

Replies generally come back into the thread automatically. If they aren't appearing, check if the sender email address (From address) is correctly set to an email that routes back to Oracle Sales or is being monitored. Also verify there are no email filtering issues. Usually, the reply should show up almost immediately in the UI thread, enabling you to continue the correspondence from Oracle Sales.