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All About CalDAV

Note: This help article applies to Surf Mail, Mail Hosting and Hosted Exchange. The available calendar and synchronization features differ depending on the mail service and mailbox type. If you are not sure which mail service you are using, you can find more information in the following article.

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

 

What Is CalDAV?

CalDAV is an open synchronization protocol for calendars and appointments. Calendar data is transferred in iCalendar format and stored on a CalDAV server.

With a full CalDAV connection, appointments can be synchronized between a server and multiple devices or applications. Changes can be sent back to the server and applied to the connected devices, provided that the server and the application being used support the required features.

CalDAV is an extension of WebDAV. However, WebDAV access or a calendar link is not automatically a usable CalDAV endpoint.

 

Difference Between CalDAV, CardDAV and ICS

CalDAV

  • CalDAV synchronizes calendars and appointments.
  • Appointments can generally be viewed, created, edited and deleted.
  • Changes can be sent back to the CalDAV server.
  • Bidirectional synchronization is possible, provided that the server and the application being used support this feature.

CardDAV

  • CardDAV synchronizes contacts and address books.
  • Contacts are stored on a CardDAV server.
  • Changes can be synchronized between the server and multiple devices or applications.

Calendars and contacts are technically separate data areas. Calendars use CalDAV, while contacts use CardDAV. Many applications configure both features together. However, it is still possible that only the calendar or only the contacts are synchronized.

ICS or iCalendar

ICS is a file format for calendar data and not a synchronization protocol. The file extension is .ics.

An ICS file can contain appointments and can be imported into a calendar application once. Later changes are not automatically applied after an import.

An ICS feed can be subscribed to as an Internet calendar. Updates can be downloaded regularly. However, the subscribed calendar is generally read-only. Appointments normally cannot be created, edited or deleted. Changes are not sent back to the original calendar.

VCF or vCard

VCF is a file format for contact data. A VCF file can contain names, telephone numbers, email addresses and postal addresses, for example. Contacts can be imported or exported using this format. Automatic synchronization does not take place.

 

Difference Between Synchronization, Subscription and Import

Synchronization via CalDAV or CardDAV

  • The data is stored on a suitable server.
  • Changes are synchronized between the server and the connected devices.
  • Appointments or contacts can be available on multiple devices.
  • Bidirectional transfer is possible.

ICS Subscription

  • An external calendar is integrated using a calendar URL.
  • Appointments can be displayed and updates can be downloaded.
  • The calendar is normally read-only.
  • Changes are not sent back to the original calendar.

ICS or VCF Import

  • Existing appointments or contacts are imported once.
  • Later changes are not synchronized automatically.
  • An import does not replace CalDAV or CardDAV synchronization.

 

CalDAV and CardDAV at Green

Surf Mail or Consumer Mail

The calendar URL displayed in Webmail is a readable iCalendar feed in ICS format. It is not a CalDAV endpoint.

The feed is used to display, subscribe to or export calendar data. Changes made in an external calendar application are not sent back to the calendar in Webmail.

Bidirectional calendar or contact synchronization 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.

 

Web & Mail Hosting and Mail Hosting

Regular Web & Mail Hosting and Mail Hosting products provide POP3 and IMAP for email. MAPI and ActiveSync are not supported.

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

IMAP synchronizes email and mail folders only. Calendars and contacts are not automatically synchronized between devices or applications via IMAP.

 

Hosted Exchange

Hosted Exchange uses Exchange, MAPI and ActiveSync technologies. Depending on the mailbox type, calendar, contact and mobile synchronization are available.

  • 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 synchronization.
  • Hosted Exchange Full provides full Exchange functionality with calendar, contact and mobile synchronization.

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

 

Displaying the Calendar URL in Webmail

Webmailer 2020

  1. Log in to Webmailer.
  2. Switch to the calendar view.
  3. Open the menu with the three vertical dots to the right of the desired calendar.
  4. Select «Links to this calendar».
  5. Copy the displayed calendar address.

Note: A displayed calendar address is not automatically a CalDAV endpoint. Check whether the address is used only as an Internet calendar or ICS subscription, or whether it also supports changes and bidirectional synchronization.

 

Consumer Mail Webmail

  1. Log in to Consumer Mail Webmail.
  2. Switch to the calendar view.
  3. Open the menu with the three vertical dots next to «Calendar».
  4. Select «Show URL».
  5. Copy the displayed calendar URL.

The displayed calendar URL is an ICS feed and not a CalDAV endpoint. It can be used for read-only subscription or for exporting calendar data.

 

Using an ICS Feed in a Calendar Application

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

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

Depending on the calendar application, interactive features may be limited. These include, for example, accepting, declining or rescheduling appointments, as well as automatically updating meetings.

 

Password-Protected ICS Calendars in Outlook

The «Internet Calendar» feature in classic Outlook for Windows does not support authentication with a username and password. Outlook therefore does not prompt for credentials when adding a password-protected ICS calendar and may cancel the subscription.

A password-protected calendar cannot be subscribed to in this way. An extension such as Outlook CalDAV Synchronizer can connect Outlook to an existing CalDAV or CardDAV server. However, it cannot turn an ICS feed into a CalDAV endpoint.

Outlook CalDAV Synchronizer is a third-party product. Green does not provide support for this extension.

Note: To configure Outlook CalDAV Synchronizer, you need a genuine and accessible CalDAV or CardDAV server, the correct server address and valid credentials. A read-only ICS address displayed in Webmail is not sufficient.

 

Support by Applications and Devices

Outlook

An Internet calendar added via an ICS address is only subscribed to in Outlook. Changes to appointments are not sent back to the original calendar.

Outlook can be connected to an existing CalDAV or CardDAV server using additional extensions. The extension does not replace the required server.

Thunderbird

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

Thunderbird also requires a genuine CalDAV or CardDAV endpoint. A read-only ICS feed does not enable bidirectional synchronization.

Apple Devices

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

The ICS address displayed in Consumer Mail cannot be used as a full CalDAV endpoint.

Android

Android does not support CalDAV and CardDAV directly through its standard features in all use cases. Depending on the device and calendar app being used, an additional synchronization app may be required.

An additional app also requires a genuine CalDAV or CardDAV server. Bidirectional synchronization is not possible with a read-only ICS feed.

 

Calendar Invitations and Meeting Requests

Appointment invitations can generally be sent and received without CalDAV. The available features depend on the email and calendar application being used.

With a read-only ICS subscription, features such as accepting, declining, rescheduling or automatically updating meetings may be limited or unavailable.

Full meeting request functionality requires a suitable Exchange service or a groupware system with the corresponding calendar features.

 

Requirements for Full Synchronization

For full bidirectional synchronization, 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 synchronization features
  • Microsoft 365 with the corresponding Exchange features

You also need an accessible server address, valid credentials and an application that supports the protocol being used.

A simple calendar link or ICS feed is not sufficient. Such a feed generally provides calendar data only for reading, viewing, subscribing or exporting.

 

WebDAV, CalDAV and CardDAV Applications on Green Web Hosting

Green Web Hosting platforms are not designed to run customer-operated WebDAV, CalDAV or CardDAV server applications. This applies to Windows Hosting, Linux Web Hosting and WordPress Hosting.

With customer-operated DAV applications, required HTTP methods such as PUT or PROPFIND may be rejected by the server configuration. For example, the message «405 Method Not Allowed» may appear while GET and OPTIONS continue to work.

On Windows Hosting, the IIS WebDAV module may process DAV requests before they reach a PHP application. Required changes to higher-level IIS modules or handlers may be restricted in Web Hosting. In this case, a change via the web.config file may result in a 500.19 error.

Disabling server-side WebDAV modules or enabling restricted IIS configuration sections for an individual Web Hosting package is not provided as a standard feature.

Note: If you want to operate your own WebDAV, CalDAV or CardDAV application, you need a server environment whose configuration you can manage yourself. Use your own server or VPS for this purpose. Standard Green Web Hosting, Windows Hosting or WordPress Hosting is not designed for this use.

 

Troubleshooting Synchronization Errors

If you experience problems with calendars or contacts, check the following:

  1. Check whether you are using CalDAV for calendars or CardDAV for contacts.
  2. Check whether this is genuine synchronization or only an ICS feed.
  3. Check whether the server address is complete and correct.
  4. Check whether the server is accessible.
  5. Check the username and password.
  6. Check whether the application being used supports the required protocol.
  7. Check whether the same account is configured on all devices.
  8. Check whether synchronization is enabled on all devices.

Note: If it is still unclear whether a calendar address supports CalDAV, first check whether the address is added to your application only as an Internet calendar or ICS subscription. If the supported features cannot be determined, 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?

No. 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?

The calendar was probably subscribed to via a read-only ICS feed. An ICS feed can display appointments but does not allow editing or bidirectional synchronization.

Why Does Synchronization 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.

Are Calendars and Contacts Synchronized via IMAP?

No. IMAP synchronizes email and mail folders. Calendars and contacts are not automatically synchronized between devices or applications.

Can an Extension Convert an ICS Feed into CalDAV?

No. An extension can connect to an existing CalDAV server. However, it cannot turn a read-only ICS feed into a CalDAV server or provide bidirectional synchronization.

Can I Connect a Google, Apple or Outlook Calendar via CalDAV?

A connection is possible provided that the respective provider offers a CalDAV service, the application being used supports it and the required credentials are available.

Can I Synchronize Contacts with CalDAV?

No. CardDAV is used for contacts. CalDAV is intended for calendars and appointments.

 

Further Information

A brief explanation of CalDAV and CardDAV can be found in the following article.

https://www.green.ch/en/caldav-/-carddav-explained

An additional guide to CalDAV can be found in the following article.

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

 

Summary

  • CalDAV synchronizes calendars and appointments.
  • CardDAV synchronizes contacts and address books.
  • ICS and VCF are file formats and not synchronization protocols.
  • A read-only ICS feed does not enable bidirectional synchronization.
  • POP3 and IMAP do not synchronize calendars or contacts.
  • The calendar links displayed in Green Webmail systems are ICS feeds and not CalDAV endpoints.
  • Bidirectional calendar or contact synchronization is not possible with Consumer Mail addresses such as greenmail.ch and epost.ch.
  • Hosted Exchange Lite Plus and Hosted Exchange Full provide Exchange-based calendar and contact synchronization.
  • A calendar application with CalDAV support also requires a genuine CalDAV server.
  • Green Web Hosting, Windows Hosting and WordPress Hosting are not designed to run customer-operated WebDAV, CalDAV or CardDAV server applications.
  • A self-operated DAV application requires your own server or VPS.