push a button to undo sending an email
I use the delay to accomplish same/similar result
Jason Schaad commented
Maybe you don't know how the internet works..... an unsend button.. wow...
Rahul Gupta commented
If you go to preferences > composing you can find a "Sending delay" option, which will allow you to undo sending an email for a set period of time.
Is that what you are looking for?