Library /sys$common/syshlp/mailhelp.hlb SET-SHOW, FOLDER, Qualifiers, /FROM_SUBSTRING  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /FROM_SUBSTRING=text

    Selects messages containing the specified text in the From: field
    of the message, where the specified text is usually a node name
    or user name. This command searches only the node name and user
    name of the sender; it does not search the personal name field.