Who is your host?
Looks lik you are using GoDaddy?
GoDaddy is one of the most problematic host when it comes to sending emails using PHP scripts. In some cases i have seen GoDaddy take ass long as a day to relay yhe email message, so it may be that the email has sent, but it just taking a little while to be delivered.
you have set the port to 80, you may want to try a different port, alternative ports for the GoDaddy smtp server are:
465, 3535, or 25
on the thank yoou page, you can add the following code:
<?php @session_start(); var_dump($_SESSION); ?>
this will write the session contents to the page, one of the session variables will contain a status about sending the email, if this is set to success than the email has been sent to the SMTP server, and it is up to the SMTP server to relay the message.