Unable to send emails from Amazon EC2 hosted website

I installed postfix in order to enable SMTP

i followed all the steps.. i was able to receive my emails on my verified email address till thrusday

but they were blank.

suddenly it stopped on saturday

the php code is executing in the same way as it use to execute earlier

    <?php
    header('Content-type: application/json');
    $status = array(
        'type'=>'success',
        'message'=>'Email sent!'
    );

    $name = @trim(stripslashes($_POST['name'])); 
    $email = @trim(stripslashes($_POST['email'])); 
    $subject = @trim(stripslashes($_POST['subject'])); 
    $message = @trim(stripslashes($_POST['message'])); 

    $email_from = $email;
    $email_to = 'abc@gmail.com';


    $body = 'Name: ' . $name . "\n\n" . 'Email: ' . $email . "\n\n" . 'Subject: ' . $subject . "\n\n" . 'Message: ' . $message;

    $headers = "From: mail <$email_from>\r\n";
$headers .= "MIME-Version: 1.0" ."\n";
$headers .= "Content-type: text/html; charset=iso-8859-1\r\n";
    $success = mail($email_to, $subject, $body,$header);
    echo json_encode($status);
    die; 

please suggest