Runbox are a good option - company and servers in Norway: https://runbox.com/

Been around since 2000. They're also working on JMAP support and are the top financial contributor to the Stalwart mail server (https://opencollective.com/stalwart) so I think they'll have a more compelling offering soon.

Also worth keeping an eye on Thunderbird pro which will also use Stalwart: https://www.tb.pro/en-US/