Found this the other day while looking alternatives to Proton.

Posteo seems like a good alternative. The linked thread shows some concerns about their privacy, but what is surprising is that they weren't recommended by PrivacyGuides because

The fact of the matter is that we have 4 excellent mailbox providers who can meet all of the requirements we’re looking for.

Well, I just had a look, they removed one as there are only three, and now as people want to avoid Proton, that leaves Tuta and Mailbox.org as alternatives: https://www.privacyguides.org/en/email/

So maybe they should add Posteo back? Anyway, that doesn't matter that much, I just wanted to share as people might be looking for alternative for Proton

Another thread: https://discuss.privacyguides.net/t/posteo-email-provider/13346/20