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

    Specifies that the output file will be a sequential mail
    file with the default file type .MAI and the protection code
    (S:RW,O:RW,G,W). The operating system places the .MAI file
    in your top level mail directory. By default, the protection
    codes of the device and directory match those of your mail file
    directory. Like the /APPEND qualifier, the /MAIL qualifier adds
    the selected message to the end of the specified file.