I am new to the Zimbra platform so I apologize for any noobness I may exhibit!

I am having a strange issue with one account on our ZCS 5.0.5. Details:
user receives email from "Joe X". User forwards email to coworker and then files mail item into folder labeled "WORK". After about 5 minutes the orignial email returns to users inbox and is marked unread again. Email is no longer in the "WORK" folder either.

It seems like this might be some sort of sync issue where Zimbra is telling the users Outlook (2003) to return the item to the inbox.

Any ideas?