I recently had to install a Comodo SSL certificate onto a Zimbra Server. Unfortunately, if you already have a certificate there is no simple way of installing a SSL certificate that you've already purchased, hence the need for these instructions.
When you purchase a SSL cert from Comodo, you'll end up with three files:
Once you have these three files, copy the first to to your /tmp directory, and copy the key file to:
Once you've done that, you need to download an extra couple of certs from Comodo, depending on when you purchased your certificate. I used the pre-March 2009 version, from here Comodo Downloads.
Once you've downloaded them, add them to the end of your ca-bundle file.
With that done, as root, run
/opt/zimbra/bin/zmcertmgr verifycrtchain comm /tmp/$hostname.crt /tmp/$hostname.ca-bundle
Providing that doesn't error out, then you're good to deploy.
/opt/zimbra/bin/zmcertmgr deploycrt comm /tmp/$hostname.crt /tmp/$hostname.ca-bundle
Switch to the Zimbra user:
su - zimbra
Then restart all zimbra services:
Your new certificates are now installed!