@Override
    StanzaHandler createStanzaHandler(NettyConnection connection) {
        return new ClientStanzaHandler(XMPPServer.getInstance ().getPacketRouter(), connection);

    }
Enable / disable backup delivery of stanzas to the 'offline message store' of the corresponding user when a stanza
failed to be delivered on a client connection. When disabled, stanzas that can not be delivered on the connection
are discarded.
xmppserver/src/main/java/org/jivesoftware/openfire/nio/NettyClientConnectionHandler.java