Yeah I have done that a few times but your assuming I am not a lazy person it is just not worth the extra steps. Not to mention privacy wise that isn't a very good idea. Especially if the email contains some confidential/sensitive information.
I was thinking it would be cool to have a native one button fix my grammar. Or maybe a spell check like interface that I can just select text and pick alternative phrases.
There would still be privacy issues that may not be acceptable for a privacy based company like Proton Mail but it could be something like this AI will never remember or save the data it is analysing.