I'm currently testing Zimbra Network Edition 4.5.5 for my organization. First I would like to say that have been really impressed with your product. It has been a much more stable and less frustrating integration into our existing eDirectoy network than a ongoing test we have been doing of one of your competitors. One thing I have noticed that I would like to pass along is that it appears that running the McAfee Enterprise Client with the Zimbra Outlook Conector may create an issue for some of your users. We've had multiple instances with users who after importing their .pst file into zimbra, the zimbra outlook connector continually performs a sync operation while outlook is open. After researching the error logs in zimbra it was found that a particular message or messages were creating sync errors. In all instances the messages resided in the Quarantine folder created in Outlook by McAfee. Our guess is that Zimbra was attempting to copy the message contents during the sync operation, but McAfee wasn't allowing total access to the folder. The issue created resulted in a loop where the contents of the message were repeatedly copied to the server. In one instance a mailbox grew from 58 mb to over 800 mb's. To resolve this issue we simply deleted the contents of the users quarantine folder from Outlook and reconfigured McAfee to no longer place messages into Quarantine. I wasn't sure whether Zimbra's engineers were aware of this problem, and didn't find it referenced elsewhere in this forum so I thought I would post it here for someone who might find it useful.
Hope the information helps and Let me know if you require anything further.