code: @Nonnull
    public static EChange removeConnectionListener (@Nullable final ConnectionListener aConnectionListener)
    {
      if (aConnectionListener == null)
        return EChange.UNCHANGED;
  
      return s_aRWLock.writeLocked ( () -> s_aConnectionListeners.removeObject (aConnectionListener));
    }
docs: Remove an existing mail connection listener.
  
  @param aConnectionListener
  The new connection listener to set. May not be <code>null</code>.
  @return {@link EChange}
  @since 1.1.0