Hi. SpamPal is open source but hasn't been uodated in many years. I doubt that it works with Oauth but I cannot test it as I haven't used SpamPal in ages. For me, the Gmail spam filter is decent enough these days.
Hi Yo Joe, I haven't touched Spampal in years so I have no idea if it would still work on a current Windows version. My guess and what you write points towards a clear no. Also, the integrated spam filters have advanced so much that I wouldn't need anything else anyway. I cannot recommend any other tool for that reason. Cheers. Daniel