I think I fixed It
It looks like if you define a file extension under "Accepted File Types:" that isn't accounted for here in attachment.php:
$extension =substr($filename,-3);
switch(strtolower($extension))
{
case "pdf": $ctype="application/pdf"; break;
case "exe": $ctype="application/octet-stream"; break;
case "zip": $ctype="application/zip"; break;
case "doc": $ctype="application/msword"; break;
case "xls": $ctype="application/vnd.ms-excel"; break;
case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
case "gif": $ctype="image/gif"; break;
case "png": $ctype="image/png"; break;
case "jpg": $ctype="image/jpg"; break;
default: $ctype="application/force-download";
}
Then no files will be transferred from incoming emails to the ticketing system. I'm still testing this, not positive yet, but this seems to be the behaviour.
Jason