FastMail

Vdirsyncer is continuously tested against FastMail, thanks to them for providing a free account for this purpose. There are no known issues with it. FastMail’s support pages provide the settings to use:

[storage cal]
type = "caldav"
url = "https://caldav.fastmail.com/"
username = "..."
password = "..."

[storage card]
type = "carddav"
url = "https://carddav.fastmail.com/"
username = "..."
password = "..."