How to create a custom send email action in Lightning? #JS_Alternatives 

Hey guys just wondering if someone can help me with this request.

I have a customer that wants to move across to LEX but has a custom send email action that pre-populates the email template, email addresses and links the email to the custom objects record once sent. When in LEX and using this action, it switches the user back to Classic view.

How can I create this send email action in LEX?

Thanks in advance