> So if you accidentally press something and suddenly the email is gone from your inbox, you want a toast with an undo button.
Why? If an email suddenly vanishes and you don't want that you don't need a popup to tell you what happened, you can just Ctrl-Z and the email comes back
No, not for email. Tech illiterate people use email. They're not going to have the reflex to Ctrl+Z, but a toast with "undo" at least gives them the information that undoing is possible, even if they're not quick enough to click on it
