When a notification is received and is not matched by any notification rule, it could be sent to a globally configured and optional fallback email address.
So, if you did not configure this fallback email address, it was possible that generated notifications, e.g. from the Event Console, were not sent to any user.
This has been extended so that you can either configure the global mail address or set and attribute for your user accounts individually. For each of your users you can now set the flag "Receive fallback notifications".
Another change: If you use the rule based notifications and have not configured any fallback contact (either globally or user), there will be a warning message displayed on the notification configuration page.
Another change: When having a notification rule that has a condition on contact groups, or any user creates a custom notification rule, and a notification was generated which had no contact group information at all, the notification was sent to ALL users, instead of none.
That was implemented this way just to be sure that the notifications are not suppressed by accident. This has been changed to be also processed like other notifications that do not match any rule. Finally these notifications will be handled with the configured fallback contacts.