Yes you can do word.salad@yourdomain with fastmail but that ius no different to other mail providers. What the above comments re fastmail is about their masked

Yes you can do word.salad@yourdomain with fastmail but that ius no different to other mail providers. What the above comments re fastmail is about their masked email service this gives addresses like <random>@fastmail.com so this is the same lockin as Apple with the same benefits of noone is going to block that domain.