I've tested Affixa as well and agree that it works pretty well. It works with the ZWC; I don't think it works with ZD, but I could easily be wrong. The basic version is free for personal individual use, however, if you want to roll it out for an organization you must purchase a license. Not that there is anything wrong with this at all. Just wanted to point it out though because sometimes with software like this the licensing gets lost in the shuffle. A user in a company goes out on his/her own and finds the software, downloads it to the network, and before you know it half the company is using it. Yes, there are ways to prevent this from happening, but these things are not always in place everywhere, across the board.
I'm still holding out hope that bug
37462 will be "fixed" and this functionality will come to the ZD. It's been an open issue for a long time, but all I can do at this point is trust the Zimbra people who say it is coming.