Convert Name to Email Address

Okay, QB Friends, I am stumped on this one.  I have a list of Supervisor Names and I am trying to convert them to email address.  Here is the example.  I have a linked field with the names.  So, I have John Smith as a connected text field.  I need his email address to be John.Smith@domain.com.

So far, I have managed to separate "John Smith" into two fields: [Supervisor First Name] "John" and [Supervisor Last Name] "Smith", but I am stumped as to how to covert this into an email address.  I have tried this text formula:

List(([Supervisor First Name]),".",(([Supervisor Last Name])),"@domain.com)")

This doesn't work and gives back .JohnSmithJohn.@domain.com
I'm stumped.  Can anyone guide me in the right direction?  Thank you!