Thank you Nghia! You got it right. My problem is solved. But, let me explain for the benefit of future readers of this post.
My Send Email widget was not available because I was in a Server Action in a Service module. When I looked in my User Interface module, the Send Email widget was available from a Server Action on the Logic tab.
I had seen references to needing an email screen in other posts but did not understand what was being said. I have other instances where I use Send Email from processes. I have no email screens. And it all works fine. Turns out what I was calling an Email or email template is what other Outsystems users call an email screen. I guess it is called a screen because it can be found on the Interface tab.
So, Email and Send Email are only available in User Interface modules and not in Service modules.