Thank you, yes I agree and I'm not interested in hosting my own mail server. I'm just realizing that I don't really understand the difference between a mail provider and a domain, and I've run into issues before with different mail protocol settings (like when I tried to connect a school outlook account to Thunderbird and couldn't get it to work because of (I think) IMAP settings).
It's something I use all the time, and I'd like to better understand how it works.