Possible forgery

[lisati]

Here's a tracking link: https://www.spamcop.net/sc?id=z6401611819zadaa8e29814c0564d802a27b7d9c499bz

For some reason, the parser is telling me, "Possible forgery. Supposed receiving system not associated with any of your mailhosts" for IP address 77.238.178.202

As near as I can make out, and unless I'm missing something, it's a genuine Yahoo server, but not one I'd normally see. What does seem odd, however, is that there's no sign of the To: or CC: headers appearing in the message source, as forwarded from one of my Outlook.com email addresses, but I wouldn't expect that to affect the parsing of the Received: headers.