we were testing zimbra-6.0.1 NE before upgrade. We have copied zimbra-5.0.9 which are working now to a separate machine, and then performed upgrade to 6.0.1. After that it worked well for a week or so, and passed first test.
Second test phase involved some of users to try to connect to it with different mobile devices. At this point we need correct certificates, reflecting different host name. I have generated certificate with SubjectAltNames, to match the name of the host it is now running. in addition to the servername which was not changed when copying to test server was done. (the server uses it's local DNS to fake it's hostname to be the same as that of the production zimbra server)
After doing this, when restarted zimbra mailbox, I encountered 2 problems. one was with error in config file.,
--- from log/zmmailboxd.out:
798 WARN [main] log - Config error at <Set name="useDirectBuffers"/>
798 WARN [main] log - Config error at <Call name="addConnector"><Arg>
It was resolved by "zmprov -l mcf zimbraMailUseDirectBuffers TRUE"
The second problem I can't resolve:
--- from log/mailbox.log:
2009-09-25 11:03:23,655 ERROR [main]  Versions - DB Version Mismatch: ours="63" from DB="52"
2009-09-25 11:03:23,655 FATAL [main]  system - Data version mismatch. Reinitialize or upgrade the backend data store.