Thanks @acf-support
I managed to work it out!
I added:
$mailResult = false;
#$mailResult = wp_mail( '[email protected]', 'test if mail works', 'hurray' );
echo $mailResult;
I then worked out I had a typo!
This line:
$headers = 'From: ' . $user_info->first_name. ' '.$user_info->last_name . ' <' . $user_email .'>' . "\r\n";
Should be:
$headers = 'From: ' . $user_info->first_name. ' '.$user_info->last_name . ' <' . $user_info->user_email .'>' . "\r\n";
Basically, the email didn’t have $user_info-> in front of it!
Now working
Cheers