Hi Veronika
Totara has the ability to monitor events and for event rules to be created that can be Subscribed to so the user is notified by email when the event rule is met.
I checked in Totara 10 and there are events for the self-registration with approval - the closest one to what you want is the account request was confirmed.
Theoretically an email will be sent to the subscriber when a user confirms their email.
regards