@Override
    NettyConnection createNettyConnection(ChannelHandlerContext ctx) {
        final PacketDeliverer backupDeliverer = BACKUP_PACKET_DELIVERY_ENABLED.getValue() ? new OfflinePacketDeliverer() : null;
        return new NettyConnection(ctx, backupDeliverer, configuration);
    }
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