Here is what you need to do:
1) Combine the intermediate ca cert with the GeoTrust root cert which you can obtain here: Download Root Certificates - GeoTrust
- make sure that the intermediate is on top and the root cert is at the bottom (open intermediate cert, hit enter, then paste the root cert there)
2) use zmcertmgr to then verify which would be something like this:
/opt/zimbra/bin/zmcertmgr verifycrt comm /opt/zimbra/ssl/zimbra/commercial/commercial.key /root/certs/commercial.crt /root/certs/commercial_ca.crt
note: commercial_ca.crt is the combined file discussed above.
3) Now you can deploy.