CAN-SPAM defines and regulates two types of emails:
- transaction or relationship messages (communications with existing customers relating to the products they currently use)
- commercial e-mail messages (communications with anyone about anything other than existing accounts and relationships)
Disclosure and opt-out apply to the second category but not the first.
This information from the FTC provides a good overview of C-S. You might also check your regulator's exam manuals to see how this topic is covered by examiners.