I do not believe that there is the capability of doing group emailing in NUC 5.3.1. If I am wrong then please tell me how to do it.

I would love it if I could mouse Contact > Email... and a dialog box would appear similar to the the File > Print with Options and query me for which contacts to email such as "Selected contacts", "Current List", or "Entire contact file". When I clicked on "Okay" then NUC would open my email client (as set in my preferences) with all the corresponding email addresses included.

Sometimes it is more appropriate and cost-effective to send email to a group of people then snail mail.