Your select tag for Subject is actually called ‘dropown’ not ‘Subject’. It will appear to your form processor as $_POST.
Change <select name=”dropdown”> to <select name=”Phone”>
The $_POST field is being put into $Tel not $Phone.
Change $Tel = $_POST; to $Phone = $_POST;
I would add too that you should probably validate the fields that your user can type into to check they don’t contain MIME codes aimed at hijacking your mailserver. Probably best to get the thing working first tho – worry about the rest later!