flexible offline messages retrieval returning false

In XMPP chat application,i am using ASMACK library 4.0.6 at android client side.

I want to retrieve offline messages when XMPP connection established. For that 1st i am checking is server having support for flexible retrieval. Server always returning false. We enabled offline module in MongooseIM server. But why i am getting false from server?

if (!offlineMessageManager.supportsFlexibleRetrieval()) { Log.i("Offline messages not supported","" + offlineMessageManager.supportsFlexibleRetrieval()); return; }

If i try with pidgin client, i am getting offline messages..