PHP mail partially working

cant send to addresses outside of domain

[d40sithui]

guys,
got kind of a crisis on my hands. My mail() function since stopped working as of 7/26. I can still send mail to addresses in my domain, but when i send anthing out to my domain (i.e) at yahoo or hotmail, the email never arrives.
Any ideas? i made a basic script, but only the middle address gets the email. any ideas

<?php
$to = "[e-mail], [e-mail], [e-mail]";
$subject = "Test mail from production";
$message = "Hello! This is a simple email message.";
$from = "khanh";
$headers = "From: $from";
$ok = @mail($to,$subject,$message,$headers);
if($ok){
echo "Mail Sent.";
}
?>

[d40sithui]

oh and i havent changed the php.ini settings or anything else. according to winSCP php.ini it was last changed in april.

[WesleyC]

Try using an e-mail client to send an e-mail via the same settings as are present in your php.ini file. If that exhibits the same symptoms, it's the server's problem and not yours.

[d40sithui]

an email client? where would i get one of those?

[WesleyC]

Thunderbird, Microsoft Outlook, Outlook Express...

Almost any Windows computer will come with Outlook Express or Outlook, and Thunderbird is freely available for any platform.

[d40sithui]

ohh i know these. but i thought you meant like email clients that would be integrated with php. i was trying to install squirrel mail but im still working on the config