Attachments Problem

Hey, first… Great Plugin.

I have added this code into my functions
function my_upload_mimes() {
$mime_types = array(
‘dxf’ => ‘application/dxf’,
‘dwg’ => ‘application/acad’,
‘zip’ => ‘application/zip’,
‘rar’ => ‘application/rar’,
‘ai’ => ‘application/ai’,
‘geo’ => ‘application/geo’,
‘pdf’ => ‘application/pdf’,
‘jpg’ => ‘image/jpeg’,
‘jpeg’ => ‘image/jpeg’,
‘png’ => ‘image/png’,
‘gif’ => ‘image/gif’,
‘bmp’ => ‘image/bmp’,
‘tif’ => ‘image/tiff’,
);
return $mime_types;
}
add_filter( ‘upload_mimes’, ‘my_upload_mimes’ );

Now the Problem:
The Admin can send every file, also for example .dxf
Any other User can not send this Files. Then comes no message or else, only the File is not attached.
I have try to every Plugins disable but nothing helps. The mistake must in the Plugin Front End.

Can you help me please?

Thanks a lot.