Purelymail: Cheap email with custom domains, 2FA

No affiliation with the service. Just a happy user. Great UI. 2FA implementation with TOTP, app passwords and backup codes. Custom domains support SPF and DKIM. Very cheap pricing at $10/year for "all-you-can-eat" with some soft limits. Looks like a one-person project but developer has been active with regular updates on the both the service status and issue tracker.