Sending email with PHP - the best headers?

[Edward]

I'm sending HTML email using PHP, currently I use the following headers in my code. Does anyone know if I should make any changes/additions to this to reduce the risk of being classed as spam? Any advice would be great.

// HTML HEADERS
$headers = "From: $fromname <$fromemail>\r\n";
$headers .= "Reply-To: $fromname <$fromemail>\r\n";
$headers .= "Return-Path: $fromname <$fromemail>\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/html; charset=iso-8859-1\r\n";
$headers .= "X-Priority: 3\r\n";
$headers .= "X-MSMail-Priority: Normal\r\n";
$headers .= "X-Mailer: php\r\n";

[ober]

Those all look fine. Keep in mind that most spam is blocked based on the content or the subject, not the headers.