That is effectively a feature/enhancement request.
It could be a setting in Admin section.
Please file your suggestion through "Ideas" section.
Setting operational at application level is a moderate risk.
The Charter of Fundamental Rights of the European Union requires senders to respect users' opt-out.
Furthermore it applies to the recipient's location, not sender.
A company based, say, in Chile or anywhere else must respect that choice if a recipient is based anywhere in the EU.
Some EU countries require users to opt-in instead of opt-out. The inclusion to a marketing database is initiated through traditional post (paper letter).
Please review the article Marketing Automation and the European Privacy Laws for details