Will not parse or output a non-MIME email eg one sent from 'mail($to, $from, $message)' with no headers section.
Some attachments will not be parsed. Some emailers use filename="pic.gif" but some use filename=pic.gif. The latter would be ignored by this script.
Some emailers change their boundary type for seperating attachments. These would be ignored by this script. Should use stripos===0 to detect "--" when parsing multiple attachments.