Someone set off a bomb close to my house. Police asked me questions about it (time, what it sounded like, etc). They noticed I had security cameras and inquired what I had. The dumbfounded look when I said Ubiquiti (they've never heard of it) and that all footage was recorded locally on a hard drive. Like they didn't understand what that meant - obviously they were looking for an answer such as "google" or "amazon" so they could just circumvent me.

Proton and fastmail you can use custom domains. I only have experience using fastmail. They provide great instructions for the settings in cloudflare (mx records, etc). My domain is purchased through namecheap.

I can receive mail on *@mydomain.com and I can send email from any thing I want ad-hoc ([email protected] or [email protected])

I thought about selfhosting as well, but the internet concensus was it can be a hassle with your email getting rejected.