When addressing a current or former U.S. Representative or Senator, address them as Representative or Senator. The same applies to State Representatives and Senators. When writing, they would still be referred to as The Honorable and their name. When introducing them at functions, it is proper to say "former Representative" so as not to confuse an audience.
I address letter to former state representative as US representative.
The salutation for a former judge is typically "Judge [Last Name]" if you are addressing them formally.
Mr. John Jones.
Many people will call him Senator as a mark of respect. In writing he could be referred to the Honorable xxxx or former Senator xxxx.
Governor. If it was a previous governor you would simply say former Governor.
No honorific is required when addressing the former chairman of a committee.
Dear Mrs. Obama,
"Your Honor" or "Mr. (Mrs.) Mayor"
Salutation for a current Ambassador is His or Her Excellency. Also Ambassador and last name of and country. I believe that since former military and President and Senators etc.....retain their title....Like President Carter.....and military usually has Ret. after the last name I think as a salutation on an Envelope it would be His Excellany John A. Gavin, Ret.
Jackie is his daughter.
The proper salutation when addressing a letter to a former president of the United States is "Dear Mr. [Last Name]." For example, if you were writing to former President Barack Obama, you would begin with "Dear Mr. Obama." It is respectful and acknowledges their status while using a straightforward, formal address.
The President pro tempore