Assuming people know how to do that, this is preying on those who don't.
It reminds me of all the nagging and lying that MS does, telling people who download other browsers that Edge is better for example. Almost everyone here with a bit of technical knowledge knows that is ridiculous. Now Edge already has 5% market share, more than Firefox though.
I agree, I'm a happy customer for several years as well. It's not the cheapest service, but it's no-nonsense and reliable.
I pointed my own domain to Fastmail and can use wildcard email addresses (like lemmy@mydomain.com) that all end in my inbox. Also my contacts are synced on the phone with Fastmail using CardDAV support, using the DAVX5 app on Android. It's really nice to have this much flexibility.