I know I can't find the country of origin from a gmail email through MTP id. What about a Yahoo originated message sent to a gmail account. I'm trying to detect a scam and I have to find out where it's originating from. Am I allowed to paste the header here so you can see it?
Generally companies like Gmail and Yahoo will have a group of people who can investigate these things. No offense, but odds are they'd do a far better job of it than you. At the very least, they can make sure to close out that account to make life marginally more difficult for the would-be scammer. Just forward a copy of the message to the security/abuse people of whichever service it originated from.