This is a new installation of CiviCRM 5.14.0 on WordPress 5.2.1
I've created a test CiviMail using one of the default templates. When I attempt to send a test mail, I get a pop-up that says "Sorry an error has occurred and your information was not saved."
Not much information here. I had a similar problem with a Joomla site five years ago but can't find my solution