lib/ews/soap/exchange_web_service.rb
def validate_version(exchange_version)
      if server_version < exchange_version
        msg = 'The operation you are attempting to use is not compatible with'
        msg << " your configured Exchange Server version(#{server_version})."
        msg << " You must be running at least version (#{exchange_version})."
        raise EwsServerVersionError, msg
      end
    end
def validate_version(exchange_version)
      if server_version < exchange_version
        msg = 'The operation you are attempting to use is not compatible with'
        msg << " your configured Exchange Server version(#{server_version})."
        msg << " You must be running at least version (#{exchange_version})."
        raise EwsServerVersionError, msg
      end
    end
Some operations only exist for certain versions of Exchange Server.
 This method should be called with the required version and we'll throw
 an exception of the currently set @server_version does not comply.