If you have to ask then maybe it's not worth. I think that wherever you go you have the chance to make something meaningful if you really want to.

Edit: I didn't realize the date at first, so the downvotes are in order. I still believed in what I said tough.

You got downvoted for accidentally raising the very good point that the e-mail does not contain enough information to allow a prospective candidate to decide what equity would be worth? I don't know who gets downvoting power around here but they sure do not have much of a sense of humor.

1) You get to downvote when you have enough karma.

2) Humorous comments do get upvoted here, but they have to be a) funny and b) intelligent. Take, for example, this:

http://news.ycombinator.com/item?id=1225654

I'm not saying that was terribly intelligent or funny (hence only 3 upvotes), but yeah.

[Edit] Two far better examples would be http://news.ycombinator.com/item?id=1268430

http://news.ycombinator.com/item?id=1268430

And right in this thread! I am humbled by their wit. :)

what does an email that has sufficient information to valuate a company look like?

That email has more than enough information to tell me that its probably a good candidate to find out more about.

An email only has sufficient information to gauge the future value of some startup if that email has been sent back in time from the future. Preferably it is still smoking and glowing blue and placed in your hands directly by Christopher Lloyd himself.

fyi: Those who have at least 200 karma points get downvoting power.