I can only second Posteo. Using their services for years now, I can confirm that Posteo is caring about security, data protection and the environment (using green energy). Also you do not need to provide your mobile-phone number or personal information and you can use standard OTP apps to secure the weblogin when you want to use 2-Factor.

I am using several accounts shared between Thunderbird on Desktop and K-9 on Android.

The only issues I have is, when sending to some US providers that still do not have TLS (“Transportwegesicherung”) implemented. In this case I have to manually deactivate the “TLS-Versand-Garantie”-option in Posteo settings, before the email can be send. Happens twice a year or so.

Maybe the Posteo suggestion gets downvoted, because their mail services indeed cost money (instead of scanning your communication and selling your data). But I find 1€ per account per month a good deal for what you get.