Email specific user roles

Or maybe Groups*
Whichever is possible to email a large group of people in the To field.

Also, are there more shortcodes to implement to just add the New Message section?

with beta version https://www.ads-software.com/support/topic/help-me-with-testing-new-version-of-this-plugin-version-5-1/ you can add just new message section

Thanks for the information.

Any idea if it would be possible to email all users defined in a group?

You can create announcement in Dashboard > Front End PM > All Announcements > Add Announcement