Official comment
On April 3, 2018, we modified the way the "opt out" bulk email status works. It is now "Transactional Only" and allows you to still send non-marketing email via automation.
An example would be a Contact that subscribes to your "10 Weekly Tips" newsletter. Delivering a product the contact has paid for can still be done using Transactional Email.
Other examples are emails that announce a change in your privacy policy, new terms and conditions, or a change of address. You have to remove all marketing information and any "call to action" elements, even things like a "click here for offers" link in your signature. The email must not have any marketing content at all to avoid violating spam laws.
As before, you can also send them individual email from the Contact Record as long as they are the only recipient. But now you can also send them email you create and certify as Transactional Email via automation.