Thunderbird Pro will offer Thundermail email service, appointment scheduling, file sharing, and maybe even AI features. Email will be hosted on German servers.
But there are workarounds like the one Infomaniak uses (I believe Proton does it too). When sending an encrypted email to a non encrypted user, a link is sent instead of the contents of the email instead. In any case, encryption at rest with user provided keys and things like that are always an option.
Emails could be end to end encrypted, so the mail server wouldnt be able to see the emails. Basicslly PGP but out-of-the-box
The problem is that basically no one uses PGP. Adoption would be hard
But there are workarounds like the one Infomaniak uses (I believe Proton does it too). When sending an encrypted email to a non encrypted user, a link is sent instead of the contents of the email instead. In any case, encryption at rest with user provided keys and things like that are always an option.
If the encryption at rest is done by the server, that defeats the point.
Also, how does the user receiving an encrypted email access it? Do they have to enter a password? How is the password transmitted to them?