On 2017-01-03 12:11, Rob Gunther wrote: > Has anyone ever seen anything like that before for SA? Does it exist > already or any type of plugin etc?
It's not SpamAssassin, but Rspamd (https://rspamd.com/) has a plugin called 'replies' that stores message IDs of outgoing mails in Redis. If an incoming mail is a reply to a known outgoing message ID, the plugin will whitelist the incoming mail. It could probably be adapted to be used in the opposite way too, to blacklist or increase score for mails that reply to unknown message IDs. Perhaps a similar approach could be used in a SA plugin. Of course this does require a database, but at least you don't have to modify the MTA's message IDs (or become the MTA).
