Sending mails does not work when safe mode activated

[quidditch]

If the server use the php safe mode, mails are not sent when a comment is posted even if the option is turned on. It is because in safe mode, you cannot use more than 4 args for a function. I had to erase the $more in this line of the function wp_mail:

return @mail($to, $subject, $message, $headers, $more);

And now it works. What is the use of $more ? Wp_mail does not seem to be documented in the Codex.