HTML Email Composing Problem.

I'm trying to use PHP to compose an HTML formatted email and I'm running into some small problems. 1) When using "Content-Type: multipart/mixed" during my testing both Thunderbird and Gmail display the plain text and html version of the email and Firefox attaches the html portion as an attachement. 2) When using "Content-Type: multipart/alternative" during my testing Thunderbird only showed the HTML portion of the email but Gmail displayed only a blank email. 3) Spam Assassin doesn't like it either way and tags the email as SPAM for the following reasons:

0.6 HTML_SHORT_LENGTH      BODY: HTML is extremely short
0.0 HTML_MESSAGE           BODY: HTML included in message
1.5 MIME_BASE64_TEXT       RAW: Message text disguised using base64 encoding

Here is the script, which I mostly borrowed from tutorials/how to examples on the web. $to="Tom Ray <lists@blazestudios.com>"; $from="Support <testing@blazestudios.com>"; $subject="Test HTML Email";

// --> plain text part of the email                     $msgtext="This is HTML Testing"; 

//--> html part of the email

$htmlmsg=chunk_split(base64_encode("This is <b>HTML</b> testing."));                                                      

//--> create boundary $sep = strtoupper(md5(uniqid(time()))); //--> create email $header = "From: $from\n"; $header .= "MIME-Version: 1.0\n";

$header .= "Content-Type: multipart/mixed; boundary=$sep\n\n";           

$header .= "--$sep\n";

$header .= "Content-Type: text/plain; charset=ISO-8859-1\n";           $header .= "Content-Transfer-Encoding: 8bit\n\n";

$header .= "$msgtext\n\n"; $header .= "--$sep\n"; $header .= "Content-Type: text/html; charset=ISO-8859-1\n"; $header .= "Content-Transfer-Encoding: base64\n\n"; $header.= "$htmlmsg\n\n"; $header .= "--$sep--"; //--> mail it mail($to, $subject, "", $header); Any help/suggestions would be appreciated.