Thanks, you are right the order of events are different and this is not aSmack problem.
Our server sends some custom stanzas back to client as an ack to let it know that what client sent was received by the server (e.g request time, send message). I was not aware of that custom stuff on our server until now. Probably I need to add a custom IQ provider to solve this problem.
BTW, I've tried the 4.0.1-SNAPSHOT but same thing happens.
Thanks for the help!