The crazy part is it's really just this simple bayesian approach that solved like 95% of the problem. Simple math that already existed. Stuff that can be explained to a high schooler. No new crazy ML/AI, none of that. Just someone stepping back and pointing out "hey, I think we can use this tool here...."
There was a lot more lower hanging fruit in those days.
Cool! :) And thanks! As you can guess I still very pleasantly remember when the feature hit and the spam issue got so much better.
I always wonder which pieces of my code from my career I'm proud of are still running somewhere. Unfortunately, it's mostly been proprietary stuff so there's really no telling.
You could do something similar and unleash it on your mailbox. The tricky part are integrations. At work, I don't even bother since interacting with the email system there is way more tricky than with GMail.