PHP Mail not being sent to yahoo mail

[rotwyla98]

[code]
$to      = "$email";
$subject = "Add a Banner Email Verification";
$message = "Dear $name,\nThank you for adding your banner.\nPlease go <a href=\"http://www.url.com/url/eval.php?e=$email\">HERE</a> to validate your email address.\n
Please use the code <b>$random_number</b> to verify yourself.\n
Once your email has been validated, your banner will be shown on the homepage until someone else replaces it.";

$header = "From: Add A Banner <[email protected]>rn";
$header .= "MIME-Version: 1.0rn";
$header .= "Content-Type: text/html; charset=iso-8859-1rn";
$header .= "X-Priority: 3rn";
$header .= "X-MSMail-Priority: Normalrn";
$header .= "X-Mailer: PHP / ".phpversion()."rn";

mail($to, $subject, $message, $header);
[/code]

Using this guide http://www.phpfreaks.com/quickcode/E-mail-Script/299.php?higlight=mail

PROBLEMS:
1) email not being sent to yahoo mail at all. ex: [email protected] wont recieve the email
2) when sent to gmail, says <a href="etc...  instead of it being the actual code.

What am I doing wrong?