it was `{S /con/con`; my memory transposed two characters. the {S was the "system message" that AOL chatrooms used to send sounds, so that sequence of characters after a newline made your computer look for that sound. It was cool if everyone was trusted to not do the /con/con, people would have email chains with the audio files on them, like a proto-napster.
My memory is a bit hazy and I don't want to look up the exact sequence, but that's close enough.