I'm using IMap to sync my mailbox between Thunderbird, Zimbra and an iPhone 3g and it mostly works fine, but I have a very odd problem I hope someone can help me solve.

New mail syncs almost instantly from Zimbra to the iPhone and to Thunderbird, but if I delete an inbox message in Thunderbird on my Windows desktop, it disappears from inbox and goes to trash as it should, however in Zimbra and on the iPhone it sends it to trash, but leaves it in the inbox.

If I empty the trash in Thunderbird, it removes it from trash on Zimbra and on the iPhone which it should.

If I remove an item from inbox on Zimbra or the iPhone it all works as expected and removes the item from inbox everywhere and puts it in trash everywhere.

I have looked at the configurations and they seem find to me, so I'm at loss as to what setting I might change to make it work properly. I'm beginning to think it might be a bug in Thunderbird. Any ideas?

Thanks in advance