As we use Zimbra at work I decided to install Zimbra Desktop for offline email, however I ran into a bit of a snag because after downloading it and following the installation instructions I had the following error message when I ran Zimbra Desktop for the first time:
Couldn't load XPCOM.
After a bit of googling around I found this article Installing Zimbra Desktop on 64bit Linux which has the following fix to install the 32-bit libraries that are (naturally) missing in my 64-bit Fedora install:
yum install -y alsa-lib.i686 libstdc++.i686 xulrunner.i686 gtk2-engines.i686<
Once I had these libs installed I could happily run Zimbra Desktop or zdesktop.