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

    Specifies that the last message you sent will be used as text
    for the reply to the message that you are reading. You can use
    the /LAST qualifier with the /EDIT qualifier to edit the message
    before sending it.