If you put an offer in the email, its probably to low. Most people, when selling domains are morons and think their domain is worth 1000x what it really is.
On the same side, I never reply to ignorant emails. I just got one over the weekend for a domain and the message subject had my domain name and the body of the email said "$$?"
I've contacted a number of people to buy domains and NEVER tell them what I want to pay, they always tell me, then I come back with a realistic figure. If its to high, I reply with "I'm not going to even make you an offer because what I believe the domain is worth and what you think its worth are on to opposite sides of the scale, but thank you for your response."
I just did this a few weeks ago for a domain. Guy wanted $2000 and ended up buying it from him for $100
