[samokan]

殿 【しんがり; との; どの】 (しんがり) (n) (1) rear; rear unit guard; (2) anchor (man); (との) (n) feudal lord; mansion; palace; (どの) ; (pol) person; Mister (mostly in addressing someone on an envelope); Mr; SP

The kanji for "dono" can also be pronounced as "shingari", "tono" and "dono".

Right now, when addressing anybody among my group through email, I/we basically use the word "dono" or "sama", but when talking directly its just "san".

I am not sure on this, but I think its a "kaku-kotoba" or use only during written form.