Hi Sergio,
There is nothing on the Defect that will trigger an email to the customer, unless you click on the Send Email icon.
When your support team receives the original email when the ticket is submitted, there are links within that email to use to respond to the issue. And when your customer receives the response, there are links in that email to allow them to reply back.
Everything can be done through the links within the emails. You don't even have to log in to ALMComplete if you don't need to - so you're not consuming a license.
Hope that helps!
