Good options exist now, including proton and skiff. Recommend checking out skiff. Everyone knows proton.
Skiff gives you 10GB free. Proton only gives 500MB.
That said we should be paying for email. If you don’t, you wind up with Gmail, where they read and analyze the contents of your email to build a profile on you and serve you ads. Moment I noped out of Gmail was when I realized they were aggregating sales receipts in my inbox and tracking the products I was buying. Wow, when did I ever agree to that? Guess it was time move on.