It's a kind of shared hosting with full ssh (non-root) access. They offer a pre-installed Roundcube Webmailer, but you can host your own one as well.

I run my own Roundcube with my own Domain and configured a maildrop instance to sort incoming mails.

So far it works as a charm. The hoster is based in Germany and I trust them to be privacy-aware.

https://www.migadu.com/en/index.html

You pay based on traffic rather than per account/domain.