To email a customer you need to follow two simple steps.
Click on the order number on the tab or search for the order number.
Within the order page, Click on "customer details" in blue on the top.
From the section that opens, click on the email Id to open your mail application or copy-paste the email ID to the desired CRM system.
You can send it across your email.
To deliver an outstanding customer experience we strongly recommend you to read customer comments whenever possible and connect with them via email when needed. This would have a direct impact on their LTV.