I used to have a custom domain setup via Google apps. Google decided to update it to something else (they changed their name several times and I lost track of the name now). I switched to iCloud+ Mail when iCloud introduced their custom domain support a few years ago. I do have notification summaries on my iOS turned on, but that's just a guilty pleasure of mine. The summarization is so bad that it's funny. I literally have the summarization feature turned on to laugh at how bad it is every time I see a new summary. Anyway, I used to be a everything-Google guy. Now, I just spread my app usage across multiple services, which I think is a win for me in the long run instead of being locked in to an ecosystem.

I also got myself out of the most of the Apple products from the Apple ecosystem too. I'm a 1Password user because I didn't want to be part of Google or Apple ecosystems.