your form is redirecting to the thank you page, so the script is sending the email to the SMTP Server, but the SMTP server is refusing to relay the message for some reason.
Who is your host?
In the Universal Email settings, what did you enter for the SMTP Server?
Some hosts may require that the from address be a valid email address for your domain, what did you enter for the from address?
Some hosts may require that the from address be sent as an extra parameter, you may need to check the Include From address as additional Parameters option on the server settings page.
On the thank you page, add the following code for troubleshooting, just before the closing </body> tag.:
php:
<?php var_dump($_SESSION); ?>
