Thanks for your reply @inX, I have seen the value of overwrite.cli.url yesterday and changed it to https://cloud.example-new.com but today I received mail notifications with cloud.example-old.com as domain again therefore it did not solve my problem.
Sorry for my late reply. I did a restart of the webserver and it is still the cloud.example-old.com domain in the mails. At the moment I am using NC 13.