I installed and tested Zimbra on a Mac laptop for a client; the client specifically wanted to sync a huge Yahoo! account and be able to delete messages when offline, then sync and have the deletions occur on Yahoo! -- which appeared to work in the initial testing after install, but hasn't worked since the client has been traveling. He does get new mail and sent messages go out properly; the messages he deletes locally don't get deleted back in Yahoo! when he syncs.
I thought that deletions should sync, but perhaps we got lucky when testing and misunderstood the capability of the product.
Any ideas or suggestions?