It freaked the hell out of me.
In retrospect, of course he knew my name. He has been delivering to my building for at least six years, and I have picked up a number of packages. While sorting mail into apartment boxes he probably sees peoples' names and remembers them. But I had never introduced myself, nor had my name (to my knowledge) come up in any conversation with him. Somehow I subconsciously expected that we did not know each others' names.
Some days I feel I really belong in a strict Edwardian society, where one cannot speak to anyone else without a formal third-party providing introductions.