Custom domain moving back to

Hi all. I have a few questions regarding use of custom domain for my blog. I have a number of email and federated subscribers that show up in stats. I also federate my blog. If I go back to using as the domain instead of a custom domain as its now set up what happens to the subscribers and the federation part of things since it’s linked to my custom domain in settings now.

Thanks! I’d like to cease using the custom domain soon but am curious about the few settings and subscribers.