Mxroute with thunderbird as a client and mail on iOS for mobile.
Unlimited domains and rock solid. Just don’t expect lots of hand holding the company focuses on making email work you have to sort out your own details. That being said they have good documentation.
2nd Mxroute.
I got the black Friday deal a few years ago.
I love using the catchall to make emails on the fly for when I sign up for different services.