This is a bug that's a little difficult to describe, but it makes Zimbra unusuable for me.
For no known reason, one of my Yahoo mailboxes is stuck apparently getting the same message over and over again and putting it under one message as part of the "conversation." The circling arrows are visible constantly on that mailbox, and there over 500 copies of the exact same email under that conversation (so it shows (541) next to the message info but every message in the conversation is the exact same one). As long as I keep Zimbra open, it keeps adding more and there is no way to stop it. I tried closing Zimbra and I treid rebooting. As soon as I open Zimbra, it starts again, frozen on that operation.
I can navigate around on other mailboxes, and they appear to be getting new mail, so the whole program isn't locked, but that mailbox is stuck on that operation and I cannot stop it.
By the way, that message is showing up as new... with a current date even though it is a year or more old. I have no idea why that particular message is the one it keeps getting.
I think that's it for me. Zimbra is a great idea. I've been looking for something that could consolidate and sync all my online e-mail accounts for a long time. The concept is great. But it's too buggy and unreliable. I keep finding new significant bugs and I have only used it a couple of days. And since it syncs, I don't feel confident that it isn't messing up my database of e-mails and maybe losing them.
So I am going to have to uninstall. I hope that it can be overhauled to make it more reliable and I appreciate your effort.