what is the harm in them making an email offer, takes 2 seconds to read it, and if you don't like their offer, ignore it
you never know, some sellers might not get any offers at all and need cash quickly and will take an offer like that
putting "no lowball offers" usually scares away legit offers too, btw
and the S2 has been out for a long time, I would expect it to get hard to sell pretty soon