The U.S. military is a hierarchical institution, and military personnel are accustomed to a being addressed formally. Using the correct etiquette when you speak to military personnel is a sign of respect. This courtesy should be given to retired officers as well as active personnel. The U.S. Code says a retired officer can use his military title. In other words, after leaving active service, personnel do not lose their status.
Address envelopes using military rank and status. Although Department of Defense guidelines state that using civilian forms of address on mail is acceptable, many retired military personnel prefer that their military rank is used as a mark of respect. Whether the rank or the name is written first depends on whether the addressee is enlisted or commissioned.
Address envelopes to enlisted personnel with full name first, then rank, then branch of service, then status--in this case retired, or ret. For instance, your envelope might be addressed to John Brown, SMgt USAF (ret.). If your letter is social rather than professional you can leave out the branch of service.
Address envelopes to commissioned personnel by rank, then the full name, then branch of service, then status. For instance, your envelope might be addressed to Maj. Jane Brown, USAF (ret.).
Start the letter by using the rank followed by last name of the recipient. For instance "Dear General Cooper." When writing to enlisted personnel it is not necessary to use the military title.
When speaking to a retired officer, use the title she held at the time of her retirement. For instance, you should greet General Smith, who is retired, by saying "Good morning, General Smith."
When addressing enlisted ranks, the correct procedure is to use civilian address such as Mr. or Ms. However, if you wish to address a noncommissioned officer by rank, you can address him as Sergeant Smith or Airman Jones.
Use "sir" or "ma'am" as an appropriate alternative to rank and last name.
Etiquette should be about making people feel comfortable, rather than imposing a formal code of behaviour. Take your cue from the individual--if she asks to be addressed informally do so. Not all retired military personnel want to be singled out with formal etiquette.
Saluting is a sign of respect between military personnel and should never be used by civilians.