You can use captcha with it. I seem to remember that was another setting as well, that stopped spammers from outside your site being able to access it. But I've forgotten what it was. I'll have a think about that.
I am getting them now, they are not going to my spam box. I am getting a few spammers who just send junk but I don't think you can stop them. Does anyone use jot form or do you think there's another better one?