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

    SS$_NORMAL         Normal successful completion.
    MAIL$_ILLCTXADR    The context block address is illegal.
    MAIL$_INVITMCOD    The specified item code is invalid.
    MAIL$_INVITMLEN    The specified item length is invalid.
    MAIL$_MISREQITEM   The required item is missing.
    MAIL$_NOFILEOPEN   The mail file is not open.
    MAIL$_WRONGCTX     The context block is incorrect.
    MAIL$_WRONGFILE    The specified file is incorrect in this
                       context.
    SS$_ACCVIO         Access violation.