Importing users on older Zimbra to ZCS 7.1

[civilwar]

How to import users account from old zimbra mailserver (Zimbra 5) to new Zimbra mailserver (ZCS 7.1) together with old mail messages?

[phoenix]

You haven't given any details about your 'old' Zimbra version (operating system and version) nor whether you're moving this to a new server nor whether you're moving from a 32bit to 64bit server. - answers to those questions would be a good starting place. Have you also searched the forums (plus the wiki and blog) for an answer to your question? There is plenty of information available on how to move from one server to another.