And for the spammers: What matters for this is whether the recipient thought they opted in. No matter how clever you think you are by pre-checking that checkbox, or hiding it in the TOS, or putting the non-mandatory spam checkbox between two other clearly-mandatory checkboxes so people think it's mandatory: If the user didn't want the mails, they're going to mark your spam as spam and you'll have the deliverability problems that you deserve.