docs: @Nonnull
    public static EChange removeEmailDataTransportListener (@Nullable final IEmailDataTransportListener aEmailDataTransportListener)
    {
      if (aEmailDataTransportListener == null)
        return EChange.UNCHANGED;
  
      return s_aRWLock.writeLocked ( () -> s_aEmailDataTransportListeners.removeObject (aEmailDataTransportListener));
    }