I used to do something similar when I ran my own mail server. Whenever I created an account for a new service, I would add an entry to /etc/aliases e.g.

    news.ycombinator.com: stirner

and sign up for the service as news.ycombinator.com@mydomain.com. If I ever left a service, I would just remove the corresponding alias and restart Postfix.

I eventually got tired of the work required to avoid spam filters and switched to iCloud Mail, so I’m glad to see this feature built in.