When an item of mail needs to be delivered the daemon is placed on a square just out of sight of the player, rushes over to the location of the player (pushing anything in its path temporarily out of its way, exclaiming "Gangway!", "Pardon me!", "Excuse me!", etc.), hands the scroll to the player ("<Hello>, <player>! I have some mail for you."), rushes back to its starting square, and disappears. If it can't maneuver next to the player for some reason, it will "throw" the scroll to the player with an exclamation of "Catch!" This all takes place within the space of one turn.
On nethack.alt.org, a user may observe other users' games. It is then possible to communicate to the player by sending mail. The player cannot send mail back to the spectator, but the # command can be used to type arbitrary messages visible to the observing user. The player does not need to attempt to execute the command, as the observer will see the message as it is typed in.
It is possible to create a mail daemon by means of wishing for a statue of it which can then be re-animated by casting stone to flesh. This is largely useless, as the resulting mail daemon will disappear in one turn ("I'm late!") unless you attack it, in which case it will disappear if you step away from it. Killing a mail daemon will automatically (and silently) genocide mail daemons, preventing future mail delivery and violating Genocideless conduct.
A mail daemon can be created when creating random demons on a special level. This is bug C343-415. These mail daemons will immediately disappear as soon as the player moves.
In UnNetHack, in addition to delivering mail, the mail daemon can also deliver one hint scroll per game (assuming that this option is enabled). This "helpful hint" behavior has earned the mail daemon the nickname "Unclippy - the helpful hint daemon" (as a pejorative reference to the infamous Microsoft Word "helper", Clippy).
It is rumoured that these strange creatures can be harmed by
domesticated canines only.
On Unix-like operating systems, a daemon is a program that runs in the background, performing various tasks such as managing log files, performing timed maintenance tasks or answering incoming network connection requests. The program responsible for receiving mail and dispatching it to the correct location is commonly referred to as the mail daemon.