code: def check_differences(self):
          logger.info("Check that mail differences are within the limits.")
          if self.conf.size_threshold < 0:
              logger.info("Skip checking for size differences.")
          if self.conf.content_threshold < 0:
              logger.info("Skip checking for content differences.")
          if self.conf.size_threshold < 0 and self.conf.content_threshold < 0:
              return
          for mail_a, mail_b in combinations(self.pool, 2):
              if self.conf.size_threshold > -1:
                  size_difference = abs(mail_a.size - mail_b.size)
                  logger.debug("{} and {} differs by {} bytes in size.".format(
                      mail_a, mail_b, size_difference))
                  if size_difference > self.conf.size_threshold:
                      raise SizeDiffAboveThreshold
              if self.conf.content_threshold > -1:
                  content_difference = self.diff(mail_a, mail_b)
                  logger.debug(
                      "{} and {} differs by {} bytes in content.".format(
                          mail_a, mail_b, content_difference))
                  if content_difference > self.conf.content_threshold:
                      if self.conf.show_diff:
                          logger.info(self.pretty_diff(mail_a, mail_b))
                      raise ContentDiffAboveThreshold