I know answer for that. None. Don’t even bother to try. It is way too risky, difficult and expensive. And if you are customer to VPS-services as DigitalCloud they don’t even allow that.
I’m a bit lost what you are after, must be a language barrier again, but if you want to get emails to Discouse, ability to answer there and send response to customer/user Discourse can already that. I reckon search term would be like email. All you need is + -address (I don’ remember fancy name of that) and at least SES by Amazon offers it, I reckon.