If you add a new email-address to your most loved email-client, Thunderbird checks if there are linked services like CardDAV address books and CalDAV calendars.
But if you don't want to add them at this point, you have to add it later manually, which means you have look for the calendar urls and have to type in your username and password again.
Please add in option in the 'new calendar' / 'new address book' dialog to import it from an existing account settings.
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