[JoshTriplett]

> require the client to do all the indexing and upload the encrypted index

Or just require the client to do the indexing and the searching, and not upload the index anywhere.

[prophesi]

Yep. Not sure how Apple/Proton implement it, but that's exactly what Tutanota does. https://tutanota.com/blog/posts/first-search-encrypted-data

[londons_explore]

And when you log in from a new device...? Do you now need to wait days while 1000,000 emails from the last decade are all downloaded and indexed?

[prophesi]

That's an issue with or without client-side encryption. Even with IMAP, you have to download the message before its contents can be searched. While subject/sender/recipient can be searched instantly with IMAP, regardless of encryption.

[pseudalopex]

This is a limitation of your client or server. Not IMAP.

[prophesi]

No, it's a limitation by IMAP that is rectified by the server/client.

[pseudalopex]

IMAP's SEARCH TEXT command is at least 35 years old.[1]

[1] https://datatracker.ietf.org/doc/html/rfc1064

[pseudalopex]

Maybe if you have that many emails and 3G only and can't load a backup for some reason.