This option is useful for users which deals with Cyrillic content and broken (or misconfigured?) Microsoft IIS web servers, which tends to not report charset correctly. This is really dirty hack, but if this option is turned on it is assumed that all servers which reports as 'Microsoft' or 'IIS' have content in Windows-1251 charset.
This command should be used only once in configuration file and takes global effect. Default is "no".