Incoming replies to your outbound emails can be seen in the Activity Panel on the Customer Screen, allowing you track the email communication history with your customer.
The email reply from your customer will show on the Activity Panel with the title Email From.
Replying back to an email
To reply back to the customer, click the reply icon which is directly underneath the activity entry.
Once you have clicked the reply icon, the email editor will appear. The editor shows the thread of previous emails that have been sent to the customer as well as any previous replies. You can enter your email response and click Send.