I've been happy with Fastmail as a GMail alternative. Been slowly moving my logins and usernames from one to the other. Only (rather significant) complaint is that since 2018, they're affected by Australia's encryption backdoor bill.
I made the move to FastMail about 4 years ago, would hate to change again, is such a pain. Luckily I did opt for my own domain name at least which should make those changes easier if I do it again.
I think the law is over-reaching and lacking in sufficient transparency, but I don't really think it would allow anything like the common understanding of "encryption backdoor"?