Add to the front page.
I had to read a forum post to learn that Zimbra was built for Linux, and might get built for Mac OSX. People shouldn't have to dig so far to learn what platform software was made for. Put the info on the homepage where people can easily see it.
Also, what server and database software does it work with? Apache? PHP? MySGL? Any talks with site control panel people (such as cPanel) about including Zimbra in their packages?