VMS Help REPLY, Qualifiers, /USERNAME  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /USERNAME[=(username[,...])]

    Requires OPER (operator) privilege.

    Broadcasts a message to all terminals at which users are logged
    in to the system (or OpenVMS Cluster), or only to the terminals
    of the specified users. Incompatible with the /ALL and /TERMINAL
    qualifiers.