In Classic, there is a Gmail icon next too the Email field that will then link-out to a new tab and allows Gmail takes over the email experience. Emailing in Gmail is helpful to our reps because they can then leverage their email templates they've built in Groove for Gmail. 

In Lightning, that Gmail icon does not appear. Is there a setting I need to activate in order for it to show up? 

Has anyone found a way to create a custom button that would allow users to email that contact via Gmail? I was able to find a solution for a custom field, but would really like it in a button. Thanks!