Similar to what gmail.com / Mailbird / Polymail and a few other email clients allow.
Outlook 365 online is offering it too. Plus option to configure time for how long you can undo sending. Visual progress bar is nice in that case.
It would be great to have this.
BTW the Gmail implementation is far superior to the Outlook 365 one.
In Gmail, you can see the message that's going to go out. This is so crucial to seeing that you have a typo or whatever that you want to fix.
In Outlook, you can't see your pending reply. You can still cancel it while that progress bar spins down.
Then if you do cancel, (Outlook again) when you go to resend, it always goes immediately.
It would be cool if Hiri did this... please do the Gmail version :)
Being hiri exchange only email client, it would make sense to implement a recall feature such as the one present on Exchange, you sent the email, you wanted recalled, click on that one option and the message disappears from the recipients' inbox, that easy.
You won't be notified about changes to this idea.