I am following procudre as i recevied given files from Comodo ,
AddTrustExternalCARoot.crt
ComodoUTNSGCCA.crt
EssentialSSLCA_2.crt
STAR_mydomain_com.crt
UTNAddTrustSGCCA.crt
When i tried to install Comodo SSL certificate from web Admin Panel ->Install Certificate ->Install the commercially signed certificate->

Certificate:STAR_mydomian_com
RootCA:AddTrustExternalCARoot
Intermediate CA: ???? what .crt require here?

Your certificate was not installed due to the error : system failure: exception executing command: zmcertmgr verifycrtkey comm /opt/zimbra/mailboxd/webapps/zimbraAdmin/tmp/current_comm.key /opt/zimbra/mailboxd/webapps/zimbraAdmin/tmp/current.crt with {RemoteManager: mail.mydomian.com->zimbra@mail.mydomain.com:22}

Please help me how to install comodo certificate in zimbra with version as below.

Release 7.2.0_GA_2669.RHEL6_64_20120410002025 CentOS6_64 FOSS edition.