PHP邮件消息问题

Question

When I try sending simple e-mails like this:

$email = '[e-mail]';
$message = 'Hello.';
$headers  = 'MIME-Version: 1.0' . "
";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "
";
$headers .= 'From: Example - No Reply <[e-mail]>' . "
";
mail($email,'Test',$message,$headers);

They work completely fine, but when I try to send a more complex message it just fails to do so :

$message = "<p>Thank you for registering with our system. In order to use it we need you to visit the following link:<br />
<a href='http://www.example.com/activate.php?q=$activation_link'>http://www.example.com/activate.php</a>
</p>"

I find this quite interesting. Is it possible that my host (iPage) has got some kind of filters that do not allow this? (Which is absurd) Or is it a mistake on my part?

Answer 1

Alright, this just got pretty obvious after more testing. I am able to send all the e-mails if I exclude my domain name, which is pretty weird.

It's possible that my hosts filter is picking this up. Going to have to see what's wrong with them.