The lack of search kills it though for me. Doesn't say anything about that for the premium tier either. But even for a small test run, no search and no IMAP so I can't hook up a search engine myself makes this largely useless to me. Sad though, it looks pretty promising.
Aside, IMAP and POP3 can guarantee end-to-end encryption. Since they aren't used to send your messages, just for you to fetch them from your provider, all you need is TLS and we're done. So it could be supported without compromising much of anything from a security perspective, though you'd lose the rest of the encryption features.
https://tutanota.com - https://github.com/tutao/tutanota - https://en.wikipedia.org/wiki/Tutanota
The company is based in Germany and benefits from BDSG.