iCal is a personal calendar application made by Apple Inc. that runs on the Mac OS X operating system. iCal was the first calendar application that offered support for multiple calendars and the ability to publish/subscribe calendars to WebDAV server.
To add a new CalDAV account (when using IceWarp Server), do the following:
Use your full email address as your username.
The appropriate URL format is: http://<server>/webdav/users/<email_address>/
Example: http://mail.icewarp.com/webdav/users/john.doe@icewarp.com/
NOTE that this format is different from the formats for the Mozilla Sunbird clients.

NOTE: iCal does not support folder hierarchy. If you wish to add shared folders and public ones, you will need to configure multiple accounts, and specify the folders used by this account under the Account URL, such as:
http://<server>/webdav/users/<email_address>/Public/Events/