docs: @Override
      protected String getToNames() {
  
          List<String> excluded = new ArrayList<String>();
          List<String> users = new ArrayList<String>();
          Iterator<String> itIds = idsList().iterator();
          while (itIds.hasNext()) {
              String id = itIds.next();
              CmsSessionInfo session = OpenCms.getSessionManager().getSessionInfo(id);
              if (session != null) {
                  try {
                      CmsUser user = getCms().readUser(session.getUserId());
                      String userName = user.getFullName();
                      if (!users.contains(userName)) {
                          String emailAddress = user.getEmail();
                          if (CmsStringUtil.isNotEmptyOrWhitespaceOnly(emailAddress)) {
                              users.add(userName);
                          } else {
                              excluded.add(userName);
                          }
                      }
                  } catch (Exception e) {
                      LOG.error(e.getLocalizedMessage(), e);
                  }
              }
          }
          if (!excluded.isEmpty()) {
              StringBuffer text = new StringBuffer(500);
              text.append(Messages.get().container(Messages.GUI_EXCLUDED_USERS_WARNING_0).key(getLocale()));
              text.append("\n");
              Iterator<String> it = excluded.iterator();
              while (it.hasNext()) {
                  text.append("- ");
                  text.append(it.next());
                  text.append("\n");
              }
              setExcludedUsers(text.toString());
          }
          if (users.isEmpty()) {
              setCommitErrors(
                  Collections.singletonList((Throwable)new CmsIllegalStateException(
                      Messages.get().container(Messages.ERR_NO_SELECTED_USER_WITH_EMAIL_0))));
              return "";
          }
          StringBuffer result = new StringBuffer(256);
          Iterator<String> itUsers = users.iterator();
          while (itUsers.hasNext()) {
              result.append(itUsers.next().toString());
              if (itUsers.hasNext()) {
                  result.append("; ");
              }
          }
          return result.toString();
      }