Preexisting Certifcate Installation for Zimbra 6.0
Zimbra makes it extremely easy to install either a self-signed certificate or a commercial certificate specific to the zimbra server. If, on the other hand, you want to install a certificate you created somewhere else (such as a wildcard certificate for your domain) the procedure is a bit more involved.
Become root, make a directory to work in, bring the files over and rename them:
mkdir /root/certs cd /root/certs