We talked about this in class, how there seemed to be these things in the Metaverse called 'demons' that seemed to be functioning as some kind of a system tool. The specific example I'm looking at is where Hiro gives one of the underground demons the Snow Crash virus 'scroll', and tells it to deliver the scroll to his office, but not to open it. Looking into real life computer applications, particularly those relating to e-mail, there are programs or utilities that are referred to as 'mail daemons'. These daemons are used as a kind of status messenger for various e-mails, and, at the time that Snow Crash was written, were a far more common utility in e-mail programming. There were even some (admittedly simple) computer games that utilized the mailer daemon. Nethack (similar to Moira, Rogue, or Angband) comes to mind; even though it was a game that was played off-line, if you knew how to sync your e-mail address with the game, and were online at the time, a character called (literally) the 'Mailer Daemon' would rush up to you and deliver you the message, after acceptance, of course. They still do exist today, but are not referred to as daemons, probably because someone complained that they didn't want to have to deal with something that was named as a d(a)emon. It mainly came around when something went wrong with your e-mail, which could be the reason behind the naming.
I'll note that the only time I've ever encountered the mailer daemon was when I would input a bad address. Other than that I never saw it.