how are you getting your email values?
you could place your emails into an array, then use foreach()
eg
$emails="you@aol.com,me@aol.com,them@aol.com";
$emailsArray= explode(",", $emails);
foreach($emailsArray as $key => $value) {
$customername = $_POST["customername"];
$contactname = $_POST["contactname"];
$customerordernumber = $_POST["customerordernumber"];
$phonenumber = $_POST["phonenumber"];
$faxnumber = $_POST["faxnumber"];
$email = $_POST["email"];
$headers = "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/html; charset=iso-8859-1\r\n";
$headers .= "From:.... \r\n";
$headers .= "Return-path:.... \r\n";
$subject = $customerordernumber;
$message = "<html><body>Hello!<br><br>The following message has been sent: <br><br><b>To:</b> $value<br><b>Name:</b> $contactname<br><b>Order Number:</b> $customerordernumber<br><b>Phone Number:</b> $phonenumber<br><b>Fax Number:</b> $faxnumber<br><b>E-Mail:</b> $email<br></body></html>";
$mailsent = mail($value, $subject, nl2br($message), $headers);
if ($mailsent) {
echo "Congrats! The following message has been sent: <br><br>";
echo "<b>To:</b> $value<br>";
echo "<b>Name:</b> $contactname<br>";
echo "<b>Order Number:</b> $customerordernumber<br>";
echo "<b>Phone Number:</b> $phonenumber<br>";
echo "<b>Fax Number:</b> $faxnumber<br>";
echo "<b>E-Mail:</b> $email<br>";
} else {
echo "There was an error...";
}
}
?>
using this method will send the email to each in the array, the recipient will only see them as the receiver no other emails will be displayed, great for members area etc which will keep details comfidential. Alternatively you could add a BCC header and send the email to your own email address, good to do first to check out the message, page layout etc.
you can also add images to you email by using <img src='http://www.yoursite.com/images/whatever.gif' width='229' height='56'>within the $message <body> tags this gives you message an extra dimension,
hope this helps