DKIM (DomainKeys Identified Mail) is "a method of email authentication that helps prevent spammers and other malicious parties from impersonating a legitimate domain". When you have completed your calendar's Custom Domain setup, your calendar will automatically reconfigure to send emails via an email address that uses your Custom Domain, e.g. noreply@calendar.organization.org. If you do not have DKIM set up, your email network will block this email address, which will prevent your users from receiving important Automatic Notifications.
To resolve this issue, your Onboarding Success Manager or our Support team (support@concept3d.com), can assist you with implementing DKIM.
DKIM implementation entails sending a set of DNS and TXT records to your web or ITS team, who can put those records in place on your end to authenticate the calendar's email address against your email network.
To get this process started, please contact your Onboarding or Partner Success Manager, or support@concept3d.com, and please let them know the point of contact to whom they can send these necessary DKIM records.