CAN SPAM exemption

Hello - can someone point me in the direction of where I can find this (exemption for communications within closed systems) in the act? I pulled this statement from another thread - "The broadest exemption, however, is for communications within closed systems. That means you can use the messaging system inside your home banking system without any concern for CAN-SPAM." Thank you!

The exemption arises from the definition of "electronic mail address" in the CAN-SPAM act. This definition is found in Section 3, paragraph 5, here: https://www.ftc.gov/sites/default/files/documents/cases/2007/11/canspam.pdf