I have had zero spam the last 8 years.
The code is ancient and runs on an even older version of lispworks with Auth details hard coded all over the place, so I the time it would take for me to share it would be longer than to rewrite it in some hip language.
Had I been lazy and not as privacy conscious I would have let Gmail do the spam filtering for me.
There is nothing technically novel about it. Heck, python even includes an SMTP server in the stdlib. You could.probably write a PoC in a couple of hours.
I'm reasonably sure the answer to your questions is yes.