This is basically just plain gpg+email done via a browser extension. So no protection of metadata (headers), no indexing of body (by upstream provider).
So if you have (potentially sensitive) information in the subject, you can search on that, and on to/from/cc etc -- but not on email body. Only way to achieve that securely, would be to have an encrypted index (that might be stored in an IMAP folder, encrypted) and decrypt and search it locally. At that point you are doing something rather different from what gmail is (currently) doing, however (I believe mailpile does something along those lines).
This is basically just plain gpg+email done via a browser extension. So no protection of metadata (headers), no indexing of body (by upstream provider).
So if you have (potentially sensitive) information in the subject, you can search on that, and on to/from/cc etc -- but not on email body. Only way to achieve that securely, would be to have an encrypted index (that might be stored in an IMAP folder, encrypted) and decrypt and search it locally. At that point you are doing something rather different from what gmail is (currently) doing, however (I believe mailpile does something along those lines).