Q. Why this form, why not post an email address?
A. I used to. In the good old days of the internet you could post your email address anywhere. Do it now and you get torrents of spam.
Q. Is my email address safe here?
A. Well *I'm* not going to spam you, nor pass your email to anyone who will, nor post your email address anywhere else. This sort of script isn't mega secure, but its should be OK. If you're worried, don't use it. There's no logging or anything, (well other than server mail system logs): no log of email addresses in my webspace some lowlife could hack into.