Earlier quoted context omitted.
I have used Fastmail for years with a custom domain without a single problem. Amazingly great communications from the company too. Highly recommended but not free. (Less than $2/month though - so almost free.)
I think half of my comments on hacker news are how much I love Fastmail, which I've used for email, calendar, and contacts for a decade now.
I need to use my account more, though. So helplessly locked into my Google account for sign ups everywhere.
Perhaps I ought to read that "The Psychology of Dread Tasks" article that is also trending now.