Then when you go to send an actual email you've given this option:
Unchecking it by passes anyone's option to opt out of site mailings.
EDIT: Helps to read your request, sorry I'll leave the info above for reference , I put a link to the privacy section to allow users to opt out that way.
That's not really adequate these days. You need to have a link in the message that auto opts them out just by clicking the link. Some email hosts want to see double opt out.