Actually, I'm following the guidelines from
DomainKeys/DKIM Implementation on Zimbra+SLES 11 SP1 with OpenDKIM | Spirit of Change &
Installing OpenDKIM RPM via Yum with Postfix or Sendmail (for RHEL / CentOS / Fedora) | Steve Jenkins' Blog to setup my DKIM signed on Zimbra.
But after all the configuration is done, I still unable to signed all my outgoing email.
Really appreciate if any experts can give me some guidance to get this up.
Thank you very much.