Fastmail

DAVdroid has been successfully tested with Fastmail.

FastMail is an email service offering paid email accounts. It also allows to manage calendars and contacts and provides CalDAV/CardDAV interfaces.

App password

In order to use 3rd-party applications like DAVdroid or Thunderbird with FastMail, you need to generate an app password. Choose "Mail, calendars and contacts" access.

DAVdroid settings

Choose "Login with email address" and enter your FastMail email address and the generated app password (see above).

Contact group method: groups are separate VCards