I am in a discussion with the developer of the Yahoo! notifier for Firefox.
My idea was to see if the notifier could be adapted to work with a Zimbra
mail server. If you want to see the details go here:

[Ext] Yahoo Mail Notifier 1.0.0.3 - discussion - MozillaZine Forums

The main thing that seems to be required to make it work is some sort of page that displays the unread mail count. Does the zimbra server produce anything that might be usable to a plugin like this?

It looks like Yahoo! has a system for its Yahoo! toolbar which produces this:

http://update.toolbar.yahoo.com/slv/v4/not

Any thoughts on getting this to work? I can see it being quite useful.