Clients like Thunderbird are great because you have everything stored locally so you can easily search offline. They also support encrypting and decrypting emails in PGP. However, they seem to have the same limitation as protonmail where you can’t search through encrypted emails.
I know that protonmail can’t just store your key at their server since that would defeat the purpose, so the emails are all ciphertext to them right? But in Thunderbird, you already have the key and decrypt everything all the time. So why can’t you skip the middleman in your local machine and store everything locally in plaintext? It’s not less secure since if your local machine is compromised, your private key is also compromised.
Or at the very least give us the option and have a slightly less secure but much more convenient option.
Point is, one can decrypt each email individually. That slows an malicious attacker rummaging in your device from finding what they are after as much as it does you.
You wouldn’t be alone in wanting this feature, but for those who need rather than prefer to encrypt, the option to store locally in plaintext is a major risk. On balance it seems better for developers to pay heed to that than to our preferences.
For the rest of us, we can download the emails we wish to refer to with ease, or we can create aides memoire to make it easy to locate specific emails later.