During an email forensics investigation, an analyst examines headers and sees `Received: from mail.evil.com (192.168.1.100) by mail.victim.com` followed by `DKIM-Signature: v=1; a=rsa-sha256; d=evil.com; s=selector; bh=...; h=...; b=...`. The email claims to be from support@paypal.com. Which finding is the strongest indicator of spoofing?