It's too late for 3.7, but something like this could be an interesting enhancement for 3.8.  I'm not so sure about the name of the suggested parameter since it seems more about recording successful deliveries in addition to the normally failed deliveries.  But we can quibble about that later.

Would you be willing and able to turn your patch into a pull request against our GitHub repo?  You would need to sign the CLA.  We're also going to want a test, some additional documentation, and a news entry.

See devguide.python.org for details.