Finally I was able to use CardDAV on my iPhone. Buggy, but once the account is setup it works in both directions.
Zimbra 6.0.7_GA_2473.RHEL5_20100616214455 CentOS5 FOSS edition
iPhone iOS 4.0.2
- Create a new CardDAV account
- Server: zimbraserver.yourdomain.com
- Username:
account@yourdomain.com
- Ignore all errors, disable the account with the slider
- Save your settings
- Advanced: Port 80 or SSL 443
- Save your settings
- Make sure all settings are still there after you left the setup page
- Make the account active, ignore the errors
Check your contacts, there's your Zimbra server.