I feel like you'd get this with the Protonmail Bridge. It acts as it a email provider on your local network, and handles the encryption stuff itself. I believe Thunderbird sees and stores the email it sees through that as plan text.
ryonia
joined 1 year ago
Smiles softly. You're welcome.
Settings -> Default panel content
Haven't used it myself, but this looks like the setting for it.
For those who don't know, shift+F10 to bring up a command prompt when using a windows install image. Can do it when it starts asking you for stuff. I know the chkdsk tools and manage-bde (the bitlocker cli) are avaliable there at least.