VMS Help CONVERT, /DOCUMENT, Qualifiers, /MESSAGE_FILE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /MESSAGE_FILE=filespec
       /NOMESSAGE_FILE (default)

    Turns on message logging for document conversion. Messages output
    by the input and output converters are directed to the file
    specified with filespec. If filespec is not specified, messages
    are output to SYS$ERROR. The default is /NOMESSAGE_FILE.