If I accidentally type an address incorrectly it gets picked up and sits there waiting to be used. And I have, as it is mostly highlighted.
Don't register every address that is being typed, I'd rather make my own decision if I wish to add it or not. Less Mailer Deamons for sure (sp?)
Click on Edit → Mail Settings > tap on Advanced tab > uncheck the option " Auto-add contacts to my Address Book when I send them mail" Changes are saved automatically.