If you really want to nitpick; if you're following this logic any email client requires an operating system so you need to add that cost to any email client you might be using. Surely you will pull out Linux? Not an option for many people, does not support many of my programs, you can keep it for now.
OE is about as free as it gets and I agree with Mark, you got to be an idiot to click the link or open an attachment with, say, *.scr extention
M