From Elendor
Syntax 1: +MGROUP/LIST [<group name>]
Without a group name, this lists all mailgroups. If given a group name, it
lists all members of that mail group.
Syntax 2: +MGROUP/EX <group name>
Gives the literal definition of the specified mailgroup.
Syntax 3: +MGROUP/ADD <name>=<address>
This is an admin-only command that creates a new mailgroup by the given name.
<address> is a list of player names, player dbrefs, and/or bulletin boards
(no other mailgroups allowed). Admins are encouraged to use dbref numbers
instead of names and to avoid naming mailgroups identically to bulletin
boards. In the event of a conflict, the mailgroup name has priority,
however if a conflicting name is used in the mailgroup <address>, it
defaults to the bulletin board.
Syntax 4: +MGROUP/REMOVE <name>
This admin-only command deletes the mailgroup specified by <name>.