Hi Sean, Seems like there are a couple possible issues: 1) Is DNS configured properly? I see some DNS related errors in your post. 2) Do you have SSL enabled for Calendar and Contacts? The errors below hint at something wrong like SSL is enabled but the certificates are not in place. Check "Server.app > Certificates > Settings > Secure services using” and choose “Custom” and set “Calendar and Contacts” to None (thereby disabling SSL for that service) . The service will take a few seconds to restart with the new setting. Then point your web browser at http://yourservername:8008/principals/ to see if the calendar server responds. Port 8008 is calendar and contacts service direct, non SSL port. Next browse to http://yourservername:80/principals and see if that works. Port 80 reverse-proxies internally to 8008 via Apache httpd so that the web calendar can function. Next go back and set the certificate for Calendar and Contacts, and after the service restarts you should be able to browse to https://yourservername:8443/principals/ (the direct SSL port) and https://yourservername:443/principals/ (the reverse-proxied SSL port). If the direct ports work but the reverse-proxied ports don’t, I can talk you through making sure the reverse proxy settings are loaded. ~morgen P.S. When you configure the calendar server’s “Enable invitations by email” option, be sure not to use a mail account that is used for any other purpose, as calendar server will delete all messages in the inbox of that account. It should be an account dedicated to calendar server. I notice you are getting IMAP login failures for that account.