PHP: the mail body is not complete after sending mail?

I am using this code to send my mails:

public function sendMail($receiver, $subject, $message){

    $header = "Content-type: text/html";

    mail($receiver, $subject, $message, $header);
}

The mail is sent, but the content ($message) is not complete when I open the mail later on. Its a pretty long text but could this be the reason? Why is the mail message cut?

Thanks!


Use newlines at the end of a header entry

$header = "From: ...\n";
$header .= "Content-type: text/html\n";
mail($receiver, $subject, $message, $header);