Without even having to check, I can see what the problem is from your X3 PHPMailer Debug output. You have left the FROM
field empty in your mail settings ... You must set this address to a valid email address, that is allowed to send based on your SMTP settings. Often, the email you add here, will be the SAME as your recipient email address. For example:
This may sound strange to you, but technically this is the way sending email from servers must work. The email must get sent FROM someone, and unlike normal emailing where an email is sent from the person who sends the email, sending from your website is technically YOU who are sending to YOURSELF on behalf of your visitors.