Add "no mail" field to user profiles

It happened recently that the marketing team sent out a mail to all typo3.org users to promote their new shop site. I wish that there is a checkbox in user profiles which lets you unsubscribe from those mails.

Additionally, I think that from a legal point of view, it needs to be clarified if such a field should be turned on or off for existing users (opt-in vs. opt-out).