How to get copy of my licence key sent to different email adress? Old email addr doesn't exist any longer.

I am managing my fathers laptop. For some reason he needs to re-activate his eM Client license key. I know how to get new license key generated and emailed to him. The dilemma is that the email adress he used to register doesn ́t exist anymore, so the new key is sent into a black hole. When I register a new account using his new email address, I get a key, but when I enter that key I get an error saying I’m breaking the license agreement.
Is there a way to get around this without un-installing (and potentailly losing all his old mails)?

You could write to eM Client and ask them to change the registered address, or simply register a new one under a different email address.