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CalDAV / CardDAV Explained

Note: This help article applies to Surf Mail, Mail Hosting and Hosted Exchange. The limitations described for operating your own WebDAV, CalDAV or CardDAV applications also apply to Green web hosting products. If you are unsure which email service you use, you can find more information in the following article.

https://www.green.ch/en/which-email-service-do-i-use

 

What are CalDAV and CardDAV?

CalDAV and CardDAV are open protocols for synchronising calendar and contact data between a server and connected devices or applications.

  • CalDAV synchronises calendars and appointments.
  • CardDAV synchronises contacts and address books.
  • Changes can be synchronised in both directions between the server and connected devices.

CalDAV is based on WebDAV and uses the iCalendar format for calendar data. CardDAV uses vCard for contact data.

CalDAV and CardDAV are not equivalent to Microsoft Exchange, MAPI or ActiveSync. Exchange uses proprietary Microsoft technologies and provides additional functions such as calendar sharing, delegation, meeting invitations and free/busy information.

 

Difference between synchronisation protocols and file formats

CalDAV and CardDAV

CalDAV and CardDAV are synchronisation protocols. The data is stored centrally on a suitable server and synchronised between connected devices or applications.

With bidirectional synchronisation, new, changed or deleted appointments and contacts are sent back to the server and updated on the other connected devices. These functions are available only if both the server and the application being used support the respective protocol.

 

ICS or iCalendar

ICS is a file format for calendar data. The file extension is .ics. An ICS file or ICS feed is not a CalDAV server.

When an ICS file is imported, the appointments it contains are transferred to a calendar once. Subsequent changes are not synchronised automatically.

An ICS feed can be subscribed to as an Internet calendar. Updates are loaded regularly, depending on the application. However, the subscribed calendar is generally intended to be read-only. Changes made in the external application are not sent back to the original calendar.

VCF or vCard

VCF is a file format for contact data. The file extension is .vcf. A VCF file can contain names, telephone numbers, email addresses and postal addresses, for example.

Contacts can be imported from or exported to a VCF file. No automatic synchronisation takes place. An import or export therefore does not replace CardDAV synchronisation.

 

What types of calendars and contacts are available?

Local calendars and contacts

Local calendars and contacts are stored on a single device only. They are not synchronised automatically with other devices.

Subscribed ICS calendars

An ICS calendar is added using a calendar link. Appointments can be displayed and updates can be loaded again, depending on the application. However, full bidirectional synchronisation and editing of the original calendar are not possible.

CalDAV calendars and CardDAV contacts

The data is stored on a suitable CalDAV or CardDAV server. Changes can be synchronised between multiple connected devices and applications.

Exchange calendars and Exchange contacts

Exchange uses Microsoft technologies such as MAPI and ActiveSync. Depending on the product and mailbox type, calendar, contact and mobile synchronisation as well as other Exchange functions are available.

 

CalDAV and CardDAV at Green

Web and Mail Hosting and Mail Hosting

Web and Mail Hosting and Mail Hosting support POP3 and IMAP for email. MAPI and ActiveSync are not supported.

Calendars and contacts can be created in Webmail. However, the available calendar addresses are iCalendar feeds in ICS format only and are not CalDAV endpoints. Bidirectional synchronisation of calendars or contacts using CalDAV or CardDAV is therefore not possible.

IMAP synchronises email and email folders only. Calendars and contacts are not synchronised between devices or applications by IMAP.

 

Surf Mail or Consumer Mail

With Surf Mail or Consumer Mail, calendar addresses in Webmail are also available only as ICS feeds. They are used to display, subscribe to or export calendar data and do not support CalDAV synchronisation.

Bidirectional calendar or contact synchronisation is not possible with Consumer Mail addresses such as greenmail.ch and epost.ch. Consumer Mail Webmail does not provide a CalDAV or CardDAV server.

Further information about the addresses belonging to Consumer Mail or Surf Mail can be found in the following article.

https://www.green.ch/en/which-addresses-belong-to-consumer-mail-/-surfmail

 

Hosted Exchange

Hosted Exchange uses Exchange, MAPI and ActiveSync technologies. The available functions depend on the mailbox type.

  • Hosted Exchange Lite is a POP- and IMAP-based solution without full Exchange functionality.
  • Hosted Exchange Lite Plus is an Exchange-based solution with calendar and contact synchronisation.
  • Hosted Exchange Full provides full Exchange functionality with calendar, contact and mobile synchronisation.

Hosted Exchange Lite must therefore not be considered equivalent to Hosted Exchange Lite Plus or Hosted Exchange Full.

 

WebDAV limitations with Green Web Hosting

Green's server and web hosting configurations are not designed to operate customer-owned WebDAV, CalDAV or CardDAV applications.

This applies to Windows Web Hosting, Linux Web Hosting and WordPress Hosting. A customer-owned application may therefore fail because of required WebDAV methods or the server configuration, even if the web application itself works in principle.

With Windows Web Hosting, the IIS WebDAV module may intercept DAV requests before they reach a PHP application. Methods such as PUT or PROPFIND may return «405 Method Not Allowed», while GET and OPTIONS work. Required sections such as system.webServer/modules or system.webServer/handlers may be locked at a higher level. Changes made using the web.config file may result in error 500.19 in this case.

The WebDAV module cannot be disabled by the customer within a regular web hosting package. The locked server sections cannot be enabled for the hosting package.

To operate your own WebDAV, CalDAV or CardDAV application, you need a server environment that you can configure accordingly. This requires your own server, such as a VPS.

Note: If your application requires WebDAV methods or changes to the web server configuration, it cannot be operated on regular Green Web Hosting. Use your own appropriately configurable server for this purpose.

 

Displaying the calendar address in Webmail

Webmailer 2020

  1. Sign in to Webmail at the following address.

https://webmail.swisshosting.ch/SOGo/

  1. Switch to the calendar view.
  2. Open the menu with the three vertical dots to the right of the required calendar.
  3. Select «Links to this Calendar».

Webmail then displays the available calendar address.

Note: A displayed calendar address is not automatically a CalDAV endpoint. Check whether the address is intended only for an ICS subscription or also supports bidirectional synchronisation.

 

Consumer Mail Webmail

  1. Sign in to Consumer Mail Webmail at the following address.

https://webmail.mail-ch.ch/

  1. Switch to the calendar view.
  2. Open the menu with the three vertical dots next to «Calendar».
  3. Select «Show URL».

Webmail then displays the calendar URL. This URL is a readable ICS feed and not a CalDAV endpoint.

 

Using an ICS feed in a calendar application

If your calendar application supports subscribing to an Internet calendar using a URL, you can enter the ICS feed displayed in Webmail.

The subscribed calendar is intended to be read-only. Appointments can be displayed. However, changes made in the external application are not sent back to Webmail.

Depending on the calendar application, other functions may be limited. These include accepting, declining or rescheduling appointments as well as automatically updating meeting requests.

 

Outlook and password-protected calendar addresses

The «Internet Calendar» function in classic Outlook for Windows does not support signing in with a username and password. Outlook therefore does not ask for credentials when a password-protected ICS address is added and cannot set up the subscription.

An extension such as Outlook CalDAV Synchronizer can connect Outlook to an existing CalDAV or CardDAV server. However, the extension cannot create a CalDAV endpoint from an ICS feed.

To synchronise using such an extension, you still need an accessible CalDAV or CardDAV server, the correct server address and valid credentials. Outlook CalDAV Synchronizer is a third-party product.

Note: The ICS addresses provided in Green Webmail cannot be converted into bidirectional CalDAV or CardDAV synchronisation by an Outlook extension.

 

Support by applications and devices

Thunderbird

Thunderbird supports CalDAV and CardDAV directly from version 102 onwards. Additional extensions such as TbSync are not required.

Thunderbird also requires a genuine CalDAV or CardDAV endpoint. An ICS feed does not provide bidirectional synchronisation.

Further information about Thunderbird can be found in the following article.

https://www.green.ch/en/thunderbird

 

Apple devices

Apple devices generally support CalDAV directly. To configure it, you need the server address and the credentials for a suitable CalDAV server.

The ICS address displayed for Surf Mail or Consumer Mail cannot be used as a CalDAV endpoint.

Further information about Apple Mail can be found in the following article.

https://www.green.ch/en/apple-mail

 

Android devices

Android does not directly support CalDAV and CardDAV through its standard functions in every use case. Depending on the device and calendar app being used, an additional synchronisation app may be required.

Such an app also requires a genuine CalDAV or CardDAV server. Bidirectional synchronisation is not possible with a readable ICS feed.

 

Calendar invitations and meeting requests

Sending and receiving appointment invitations is generally possible without CalDAV. However, the available functions depend on the email and calendar application being used.

With an ICS-only subscription, not all meeting-request functions may be available. Accepting, declining, rescheduling or automatically updating meetings may be limited or completely unavailable.

For full collaboration using meeting requests, you need a suitable Exchange service or a groupware system with the required calendar functions.

 

Requirements for full synchronisation

For full bidirectional synchronisation of calendars and contacts, you need one of the following technical solutions:

  • a genuine CalDAV server for calendars
  • a genuine CardDAV server for contacts
  • Hosted Exchange with the corresponding synchronisation functions
  • Microsoft 365 with the corresponding Exchange functions

A calendar link, ICS file or ICS feed is not sufficient. These provide calendar data only for importing, reading, displaying or subscribing.

 

Checking synchronisation problems

If calendars or contacts are not synchronised as expected, check the following:

  1. Check whether you are using CalDAV for calendars or CardDAV for contacts.
  2. Check whether the specified address is a genuine CalDAV or CardDAV endpoint or merely an ICS feed.
  3. Check whether the same account is configured on all devices.
  4. Check whether synchronisation is enabled in the applications and on the devices being used.
  5. Check the server address, username and password.
  6. Check whether the Green service being used supports the required type of synchronisation.

Note: If it is still unclear which functions a calendar address supports, contact Support and provide details of the Green product being used, the calendar application and the displayed calendar address.

 

Frequently asked questions

Can I configure an ICS address as a CalDAV account?

No. An ICS address provides calendar data but does not replace a CalDAV server.

Can I edit appointments in a subscribed ICS calendar?

A subscribed ICS calendar is generally read-only. Changes are not sent back to the original calendar.

Why can I see the calendar but not edit appointments?

In this case, the calendar was probably subscribed to as an ICS feed. An ICS feed can display appointments but does not permit bidirectional synchronisation.

Why does synchronisation not work despite CalDAV support?

Support by the application alone is not sufficient. You also need an accessible CalDAV server, the correct server address and valid credentials.

Can an extension convert an ICS feed into CalDAV?

No. An extension can connect to an existing CalDAV server. However, it cannot create a CalDAV server from an ICS feed.

Are calendars and contacts synchronised using IMAP?

No. IMAP synchronises email and email folders. Calendars and contacts are not automatically synchronised between devices or applications.

Can I operate my own WebDAV, CalDAV or CardDAV server on Green Web Hosting?

No. Green's regular web hosting platforms are not designed to operate such applications. Use your own appropriately configurable server, such as a VPS.

 

Further information

Detailed information about CalDAV can be found in the following article.

https://www.green.ch/en/all-about-caldav

A supplementary CalDAV guide can be found in the following article.

https://www.green.ch/en/caldav