We have currently a Zimbra 7.1.3 GA Open Source Edition server, deployed under an Ubuntu 8.04.4 LTS x86_64 based server.

We would like to migrate it to an Ubuntu 10.04 LTS x86_64 based server, running Zimbra 7.2.0 GA Open Source Edition.

My question is : what should I update first ? The OS (Ubuntu) or Zimbra ? Also, if I update Zimbra first and then Ubuntu, should I reinstall/re-update Zimbra later, as then Zimbra will be based on a package meant to be installed under Ubuntu 8.04 and I'll be using Ubuntu 10.04 ?

Does someone had that sort of problema before and would like to share experiences ?