ok then I found the solution. It's simple I just need to send email ask for every user password. And I could use imapsync to copy their mailbox to the new server (I don't know why its difficult just to copy user mailbox from my zimbra 3 server to new zimbra 4 server). Next time, I would think twice installing zimbra on the new server. Installing from scratch I think much better, although it will not have nice administrator web UI like zimbra.
Thanks anyway.
