Email client feature request: I want to be able to schedule emails to send, but if a new reply in that thread comes in then don't send the email

@levisan oh I like this idea!

@airsick A use I have run into multiple times is I don't want to set the expectation that I check email outside of work hours (in part because it's true but also in part so that people will not _only_ email me if it's urgent) so I'll schedule replies to appear to be sent at "normal" random times.

But then my boss—who is fine with being known as someone who emails all hours of the night—might reply in the thread after I've scheduled my reply and render what I said no longer relevant.