Stockhocker already said Mark's e-mails seems legit. It makes sense since Mark initiated the e-mail and got a response. Unless the e-mail address of Brandhuber is either fake or has been intercepted, i cannot see how it could be fake.
Don't know about art's, tohugh if it's "spoofed' it does not mean Art is to blame.
I have total confidence that Stockhocker is legit, even though i only know him thorugh the boards.