If you are scheduled to meet the Secretary of State, it is important to know how to address her and show adequate respect and sensitivity towards her status. While some important people may prefer a more casual way of communicating, it's nonetheless important to begin each meeting by assuming that the interaction is highly formal.
Stand until the Secretary of State sits down and gestures for others to do so. Although this isn't a strict protocol, it's nonetheless a sign of appropriate respect for a high-status person.
Address the Secretary of State as "Madame Secretary" if the position is held by a woman, or "Mr Secretary" if held by a man.
Always introduce the Secretary of State as "The Honorable..."
Address envelopes to:
The Honorable
(Person's full name)
Secretary of State
Washington, D.C. 20520