I am with Telekom in Germany. I just moved out and got my first ever „own“ internet connection/contract, so no hidden treasures there. What I did learn is that the e-Mail Account that you also used to get from your ISP still works and that my parents have been using that email address for the past ~18 years.

> my parents have been using that email address for the past ~18 years.

I feel this. My mom has been complaining to me lately that her email makes her reset her password every time she logs in. She's still using an ISP email account from a company that got merged into AT&T years ago, but she doesn't want to change it because it's the email everyone has. I looked into forwarding it to another email, but of course they charge a monthly subscription for that feature.