Edit: just realized you said US based. Tuta is not US based so that might not work for you. Sorry about that.
Tutanota (now just Tuta) allows you to use your domain. I use it, it doesn’t support external clients (Outlook, Thunderbird, etc.) but they do have Android, Linux, Windows (maybe Mac too) clients.
It’s also cheap.
I’ve been using it for a few years now, it works for me.
You can get a free account to check it out first and if you like it just upgrade to get the personal domain usage and increased storage limit.
I have one of these and a dumper.
I took all of the games we have and dumped them onto an SD card. I use it for the second switch we have that our kid uses.
No messing about with swapping cartridges and taking a chance on losing one, which has already happened once.
I ended up with a V2 which is even better. No wear and tear from popping the cartridge in and out and all the games on it.
Aside from the “inconvenience” of having to push the button to roll through the games, it was worth it.