Kindly advise me as to how to address an Under Secretary of State who is also an ambassador. Would it be Mr. Ambassador or Mr. Secretary?
Dear Thank you,
Persons with dual titles are addressed by the higher ranking title. An ambassador is considered higher ranked than an under secretary, so he would be addressed as Mr. Ambassador or Ambassador Smith. If female, the salutation would be Madam Ambassador or Ambassador Smith.
Because an under secretary is below the rank of Secretary, the salutation for an under secretary (with no other title) would be simply Mr. Smith or Madam Smith.
For more information, see the U.S. Department of State, "Protocol for the Modern Diplomat," http://www.maxwell.af.mil/au/awc/awcgate/state/protocol_for_diplomats.pdf