Oh, I tried it and it does encrypt it. you use this extension and it uses a keychain on that extension. The text is encrypted and the extension kinda draws on top of the mail you were reading making a little window with the unencrypted text after you input your password. I think it's glitched for me rn tho since it doesn't encrypt it when I mail myself but it might be spmething silly, I've not really tried that hard to fix it. Well either that or it works it mysterious ways.