Best bet would be to setup postfix or opensmtpd as an open relay. Just make sure it is only accessible in trusted networks though!!
https://docbot.onetwoseven.one/services/postfix/
You’d want to set the listen address to 0.0.0.0 and use a non-loop back interface.
Honestly, you’re not going to have a lot of luck with recent games. The sandybridge i5’s were great back in the day but their time has come. I had a 2600 for a looong time but it’s been out to pasture for a couple years now.
Check out the “patientgamers” communities, they like to play older games that would run a lot smoother on your hardware.