Upon connecting, a client will be sent a list of who's online on
the local BBS as well as other systems (if you and they are set
up for instant messaging). Updates will be sent for subsequent
events (logon, update, logoff).

Mostly intended for use by local consumers; you probably don't
need to open any ports for this.

Nothing uses this at the moment and you do not need to add it
to your config. Eventually it'll bring interBBS presence and
messaging back to webv4 and probably introduce a fancier textmode
imsg module.