mail() headers

[Anon]

I have two servers with identical setup, one is able to send mail to my yahoo account and the other is not.

What headers do I need so that my ISP dont badlist my mail ?

Here is my test program :

<?php
if ($send == "x") {
echo "<br>mail(".$to.",".$mess.",".$headers.")";
if (mail($to,$subj,$mess,$headers)) {
echo "<br>Mail returnerte true";
} else {
echo "<br>Mail returnerte false";
}
} else {
?>
<form action="smtp_mail.php">
<table>
<tr><td>
Til :
</td><td>
<textarea cols="80" rows="2" name="to"></textarea>
</td><tr><td>
<tr><td>
Subject :
</td><td>
<textarea cols="80" rows="2" name="subj"></textarea>
</td><tr><td>
<tr><td>
Text :
</td><td>
<textarea cols="80" rows="2" name="mess"></textarea>
</td><tr><td>
Headers :
</td><td>
<textarea cols="80" rows="8" name="headers"></textarea>
</td><td>
<input type="hidden" name="send" value="x">
</td></tr><td></td><td>
<input type="submit" value="Send mail"></td></tr>
</table>
</form>
<?php
}
?>

[Anon]

It is a good idea to add a valid pop box as a sender. Since i have quite some problems with the native mail() function of php i use the following :

function n_mail( $from, $to , $subject,$core_msg, $add_header)
{
$cmd_line=sprintf("/usr/sbin/sendmail -r %s -t",$from);
$fp=popen($cmd_line,"w");
$temp=sprintf("To: %s\n",$to);
$len=strlen($temp);
$ret_p=fputs($fp,$temp,$len);
$temp=sprintf("Subject: %s\n",$subject);
$len=strlen($temp);
$ret_p=fputs($fp,$temp,$len);
if ($add_header != "")
{
$temp=sprintf("%s\n",$add_header);
$len=strlen($temp);
$ret_p=fputs($fp,$temp,$len);
}
$temp=sprintf("\n%s\n",$core_msg);
$len=strlen($temp);
$ret_p=fputs($fp,$temp,$len);
pclose($fp);
}

This has been used with no problems in several servers and with destination accounts in most well known free email sites (hotmail, yahoo etc) and quite some ISPs.
Have in mind this code is not mine ! Ihave seen it my self somewhere (php.net maybe ?) but i dont remember where.