Carddav servers allow you to store your contacts information on a server and synchronize it with multiple devices such as mobile, desktop etc.
Hexamail fully supports CardDav.
CARDDAV
Contacts
URL
When using a carddav server or service you should be provided with a CARDDAV url that allows access to your contacts.
Check with your service provider or server admin for the correct URL to access your contacts.
Typically it will be something like (FOR EXAMPLE!):
https://www.mycontactsprovider.com/contacts/dav/
https://sync.memotoo.com:443/calDAV/
Username
The username or login required by your carddav provider to access your contacts.
login
Password
The password used to authenticate for this account