Custom domains

hannum43 wrote:

What’s a custom domain and is it better to use?

My philosophy is why complicate things—keep it simple.

Use Custom Email Domain with iCloud Mail

Set up a custom email domain with iCloud Mail on iPhone

Personalize iCloud Mail with a custom email domain and ...

I have the same question: is it a domain name that I can fully choose or does it come from a list of domain names which Apple offers out?