Re: "Jang's PoC code pertains to a recently disclosed vulnerability that's being actively exploited"
Indeed. It was a zero day patch, not a patch based on PoC. The hack was already active and in use.
Any admins that havent patched by now shouldnt be running their own email server. Just have a look at all the 404s in your logs for the exploit pages, thise are probably now being looked for by the script kiddies.