These instructions are for configuring a new Calendar account on iOS for iPhone, iPad and iPod Touch. The version of iOS used for these instructions is iOS v6.0, but they will probably work or help with other versions of iOS.

You need VPOP3 v6.0 or later for this to work. Note that a known issue in VPOP3 v6.3 may cause authentication problems - this should be fixed in VPOP3 v6.4.

1. In iOS go to Settings, then Mail, Contacts, Calendars
2. In the Accounts section, click Add Account…
3. Choose Other
4. Choose Add CalDAV Account
   1. In Server enter the VPOP3 server IP address or DNS host name, eg 192.168.1.1
   2. In User Name enter the VPOP3 account name
   3. In Password enter the VPOP3 password
   4. In Description enter a description you want to use, eg “My VPOP3 calendars”
   5. Press Next
   6. You will see a Verifying screen. This may display warnings about being unable to verify the server identity or being unable to connect using SSL. Press Continue if you receive these warnings
   7. You will probably then see a popup saying Unable to verify account information, this is normal because VPOP3 is not a calendar server which Apple have pre-configured into iOS. Press OK at this popup window.
   8. There should now be an Advanced Settings button you can press on the account dialog in iOS. Press this.
   9. In the Advanced Settings enter:
      1. For Use SSL, you will want to turn this Off unless you have configured your VPOP3 with an SSL certificate (VPOP3 Enterprise only)
      2. For Port, enter 5108 or whichever other port number you are using for the VPOP3 Webmail service
      3. In Account URL enter, http[s]://<server address>/dav/users/<username>/. Use http or https at the beginning as appropriate. eg http://192.168.1.1/dav/users/fred/
      4. Press the Back button labelled CalDAV
   10. Press the Next button. Hopefully lots of ticks will appear, and the dialog will disappear if you have entered the details correctly

If you now go to the Calendars app in iOS, you should see the VPOP3 calendars listed when you press the Calendars button.