Specifies that all .MAI files be moved from your SYS$LOGIN
    directory to the specified subdirectory.

    The SET NOMAIL_DIRECTORY command specifies that all .MAI files be
    moved from the subdirectory back to your SYS$LOGIN directory.

    The SHOW MAIL_DIRECTORY command displays the name of the device
    and directory containing all your .MAI files.

    Format

      SET MAIL_DIRECTORY  [.subdirectory-name]

      SET NOMAIL_DIRECTORY

      SHOW MAIL_DIRECTORY