mail（）阻止JSON响应

I am using the following jQuery code to send form data to a PHP handling script which either enters a new listing in a data base or updates an existing listing.

The site lists boats and yachts for sale. It is/was working great, but now the client wants to get a email notice when a new boat is listed. I added code to the PHP handling script to do that, but if I use mail() for some reason it stops the success function from working in the jQuery code below.

The mail() function is the only thing that effects it. If I comment that line out it works again.

Any ideas of what is happening?

$.ajax({  
        type: "POST",  
        url: "scripts/listing_form_json_exec.php", 
        dataType: 'json',   
        data: JSON.stringify(dataString),
        success: function(data) { 
            var yacht_id = (data);
            $('#manage_images_link').attr('href', 'manage_images.php?yacht_id=' + yacht_id);                
            $('input[name=yacht_id]').val(yacht_id);
            $('img.saved').show();
            $('img.saved').fadeOut(3000);
            $('div#button_frame').show();
            $('#errors_container').html('');

        } 
    });

EDIT

The PHP script is very long, but here is the offending part

    $_SESSION['SESS_YAUCHT_ID'] = $yacht_id;
echo json_encode($yacht_id);

if (isset($message)) {
    //mail($to, $subject, $message, $headers);
}

I tried putting the mail() function in different places, but no matter where I put it the same thing happens. Above I have the mail() function commented out and everything works. If I uncomment it the script stops working.

Try:

$_SESSION['SESS_YAUCHT_ID'] = $yacht_id;
echo json_encode($yacht_id);

if (isset($message)) {
    if(@mail($to, $subject, $message, $headers)){
            //ok
    } else {
            //error
    }
}

It turns out that since I was testing locally, it wasn't connecting to the mail server, once I uploaded it to the server everything works.

Thanks for the suggestions, as it turns out it was something silly.