Why is Delete unavailable for a calendar or address book?
You may need to use your provider's website or online account portal to delete a calendar or address book from your account. The options in BusyCal and BusyContacts depend on the account type, ownership, and permissions. When deletion through the app is not supported or permitted, Delete may be unavailable and the app may offer Unsubscribe or Stop Sharing instead. This is expected behavior.
Unsubscribe stops syncing the calendar or address book in the app. It does not delete the server copy or its events or contacts. Unchecking a calendar or address book only hides its contents from view and keeps it syncing.
To delete the server copy, sign in to the provider's website and manage it there. If the website also has no delete option, contact your account administrator or the provider's support team to check its permissions and whether it can be deleted.
Office 365 Address Books
BusyContacts can only unsubscribe from address books connected through Office 365 (Microsoft Graph), including ones you created in BusyContacts. For deletion, use Outlook on the web or your Microsoft 365 account portal. If Outlook does not offer deletion either, ask your Microsoft 365 administrator or Microsoft support for help. See Deleting an Office 365 Address Book.