I stumbled upon a great MacWorld article about email security. One of the points they make is how easy it is to run SSL security using Mail.app and a .mac account. I've been using SSL for some time and it does make me breath a bit easier considering how often I communicate with client via email. I've also routed all of my mail accounts through my .Mac account so everything is nice, clean and secure.
Anyway, you can check out the article right here.