/sys$common/syshlp/helplib.hlb MAIL Command, Qualifiers, /SUBJECT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SUBJECT="text"

    Specifies the subject of the message for the heading. If the text
    consists of more than one word, any spaces, or nonalphanumeric
    characters, enclose the text in quotation marks.