I think Satoshi didn't have too much security on his e-mail by purpose.
In fact maybe he waited for someone to hack his e-mail... so this be a warning for him. If someone was after him, the first logical step is to attack his e-mail.
Also he did left his e-mail just like that, because it is better to left it, than to delete it... after all it doesn't matter. Because everything is already recorded somewhere at the NSA servers. Or maybe it does matter, maybe Satoshi knows more than us about security and how NSA records information.
Also if Satoshi was smart, he would not just use Tor. We all know Tor can also be compromised... and if someone really wants to find you, Tor would not stop him.
I think the creator of bitcoin did get security very seriously. After all he did invent bitcoin and it is the most secure payment system on the planet.