phpMailer not sending emails to external domains
===

I am able to send emails to email addresses on the host domain so sending an email to me@domain.com work, where the mail host is domain.com, but if I send it to me@gmail.com it doesn't come through, and I don't get any errors from the phpMailer, with debug on, it shows everything has been done.  Here is my phpMailer setup:

	require_once("class.phpmailer.php");					
	
	$mail = new PHPMailer();
	$mail->IsSMTP(); // set mailer to use SMTP
	$mail->SMTPDebug = 2;
	$mail->Host = "mail.mydomain.co.uk"; // specify main and backup server					
	$mail->SMTPAuth = true; // turn on SMTP authentication					
	$mail->Username = "sendmail@mydomain.co.uk"; // SMTP username					
	$mail->Password = "password"; // SMTP password					
	$mail->From = "info@mydomain.com"; //do NOT fake header.					
	$mail->FromName = "Me";					
	$mail->AddAddress("you@gmail.com"); // Email on which you want to send mail											
	$mail->Subject = "Just a Test";					
	$mail->Body = "Hello. I am testing <b>PHP Mailer.</b>";
	
	if(!$mail->Send()){
	
		echo $mail->ErrorInfo;
	
	}else{
	
		echo "<p>Thank you, we will be in touch shortly</p>";
	
	}

What is going on?  As far as the mailer is concerned it has sent because I get back

    SMTP -> FROM SERVER:250 Requested mail action okay, completed 
    SMTP -> FROM SERVER:250 Requested mail action okay, completed 
    SMTP -> FROM SERVER:354 Start mail input; end with . 
    SMTP -> FROM SERVER:250 Requested mail action okay, completed 

