I am trying to find new email provider for my family and would appreciate some help

Hi, we are trying to find new email provider for our rather large family, but it turns out to be quite the headache and I am nowhere near to choosing one.

I am looking for european based (we are residents), privacy focused provider with affordable family plan, custom domain and not deleting our data after short time of innactivity (best I found is 6 months, but that I think is still rather short, no?). I am looking for, not anonimity, but privacy with automatic end-to-end encryption (wife or kids wont remember to click a thing with each email) and with zero-access policy. I am looking for company that has been around for over 10 years and is sustainable (ideally no free tier). Something we could preferably use with thunderbird.

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My shortlist and why it doesn't work for me:

- Proton (pricey, all in one solution and ai)

- Tuta (lock-in, not openPGP, deletion after 6 months)

- Fastmail (not opensource, no zero-access policy, not really encrypted, us based and hosted, deletion after 6months)

- Posteo (no custom domain)

- Mailfence (not opensource, encryption needs to be toggled on per email basis, no family plan, deletion after 6 months, i really dislike their marketing communication)

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Is there some provider I missed? Am I understanding something incorectly?

The service seems great and well priced, but how is Fastmail privacy email? Isn't it just on trust basis without true technical enforcement?

I don't like my choises, but I am currently deciding between Mailfence and Fastmail. Anything I missed, misunderstood or should treat differently?
Thanks for the advice, Best