#VivaldiMail works great already but it's still fairly new, still lacking some features that Opera Mail (M2) had. Opera Mail still works by the way, you can find it on https://ftp.opera.com/ftp/pub/opera/mail/1.0/ ... it's not like there has been a lot too much change in email standards. But I prefer the integration with #vivaldibrowser into one package.

What's pretty good is that the mail devs interact with the community on the forum quite a bit - the benefit of a small dedicated community.