It's working for me. Setup took a couple of tries though.
On the iPhone under OS 3.0, I Clicked on the Settings icon, Selected Mail,Contacts,Calendars->Add Account->Other->Add CalDAV Account.
I put in mail.myzimbraservername.com,
user@myzimbraservername.com, the password for the account. I did not change the automatic name it put in. It gave an error that SSL was not working, do you want to setup non-ssl? I checked yes (Strange since it is SSL on my Zimbra server) I clicked Advanced, and clicked on the Account URL and took out the :8008 it put in as a port in the url, and changed http to https. This automatically changed the ssl port to 443 and turned it on on the top of the page. I clicked next and it checked and passed the account. Calendars worked!
Checking the account after setup, My url ended up being
https://mail.myzimbraservername.com:...servername.com
Note: On the main calendar on the iPhone, if you click on the Calendars (tab) at the top it goes back a page and allows you to select the calendar or calendars to view and use.
My Zimbra server is 5.0.16 Open Source, setup with https
- Rob