The Thunderbird email client supports CalDAV calendars as standard. This can be used to access VPOP3's CalDAV server.

To add a VPOP3 CalDAV calendar to Mozilla Thunderbirdis straightforward

1. Add the calendar to Thunderbird
   1. In Thunderbird, go to File → New → Calendar
   2. Select On the Network, press Next
   3. Select CalDAV, in the Location box enter the URL for the calendar. For the user's default calendar, this will be http://<server address>:5108/calendar/<username>/default, eg http://192.168.1.100:5108/calendar/postmaster/default/. Press Next
   4. Enter a name (for your reference), colours, etc for the new calendar, and press Next
   5. Press Finish
   6. Now the calendar should appear if you go to Events and Tasks → Calendar. If you have multiple calendars defined in Lightning, then you can select which ones are displayed using the list on the left of the page