VMS Help MAIL Routines, MAIL$SEND_MESSAGE, Condition Values Returned  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    MAIL$_INVITMCOD    The specified item code is invalid.
    MAIL$_INVITMLEN    The specified item length is invalid.
    MAIL$_MISREQITEM   The required item is missing.
    SS$_ACCVIO         Access violation.
    Any condition value returned by $CONNECT.