code: protected void officeManagedLogging(Postcard postcard, String bodyFile, OptionalThing<Locale> receiverLocale) {
          final String systemTitle = PostOffice.LOGGING_TITLE_SYSINFO;
          postcard.officeManagedLogging(systemTitle, "dfmail", bodyFile);
          postcard.officeManagedLogging(systemTitle, "locale", receiverLocale.map(lo -> lo.toString()).orElse("none"));
      }
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