Mail - stop storing recipient email addresses?

I find myself clearing out the previous receipient list often as it can lead to sending emails to the wrong person.

Is there a way to stop mail from storing them in the first place?

Thanks

Well, you can disable address completion entirely in the Mail prefs, but that also turns off completion of addresses in your address book so it might be more limiting than you want. Otherwise it might be possible to figure out where Mail saves the previous recipients and set the permissions to that file so Mail can't write to it, but I wasn't able to find such a file with a quick look in the more likely places.