Took WSV's advice, and got a little further with my accounts.xml and Linux install: - Remove <guid> lines in accounts.xml - Let caldavd generate proper guid's (as per Wilfred's comments on guid formats) - Copy generated guids into <guid> tags in accounts.xml - Remove calendar info (in my case, I've put it in /var/cache/ CalendarServer/) - Delete/re-create account in iCal I still get: [caldav-8009] [-] 'No principal found for UID: admin' [caldav-8009] [-] "Attempt to create clone '/var/cache/CalendarServer/ principals/__uids__/admin' of resource <DirectoryPrincipalUIDProvisioningResource: /var/cache/CalendarServer/ principals/__uids__>" for each user in my accounts.xml (not for resources/locations). Calendars now seem to behave a bit better - I can add events without getting previous access not allowed dialogs (used to get them immediately) and names check (i.e. adding an attendee called "sonja" puts a checkmark, where Sonja is a valid account in accounts.xml and I am not using OpenDirectory) However, I now get one new error, as soon as I add an attendee: [PDClientAddressWrapper] GetClientAddress(host='127.0.0.1', port=41007) [PDClientAddressWrapper] result = AmpBox({'_answer': '6', 'host': '216.x.y.z', 'port': '4666'}) [CalDAV Outbox POST] Originator: mailto:david@thinkcreatesolve.com does not match authorized user: /principals/__uids__/ f80ea124-2bd2-5e51-b88c-bd81e65831aa/ At the point where I click "Done" on the new event, I then get the access denied message: ---- Access to "test event on home cal" in "calendar" in account "Home Calendars" is not permitted. The server responded: "HTTP/1.1 403 Forbidden" to operation CalDAVScheduleEventQueueableOperation. ---- Although in the caldavd console, the event POSTs, PUTs, and it writes the .ics file. Editing or moving the event afterwards does not generate any errors. So, 3 errors: 1. No principal found for UID (each user) 2. Originator email address does not match authorized user 3. Access is not permitted to new events The system is open at https://www.thinkcreatesolve.com and the users are admin/admin, david/david, sonja/sonja Thanks for the help! David.