@Override
    public Duration getMaxIdleTime() {
        return ConnectionSettings.Client.IDLE_TIMEOUT_PROPERTY.getValue();
    }
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