EQ Forum Admin
Something trying to identify itself as your domain was accepted by you.What is BigFish?
Received: from 1RMCEXC1.your-domain ([18.104.22.168]) by mail2.your-domain with Microsoft SMTPSVC(5.0.2195.7381);
Tue, 26 Oct 2010 18:00:17 -0400
These were the last headers recorded by your mail server.
You can only trust the email headers created by your mail server -- all the rest could be forged.
BigFish appears to be Microsoft hosted Exchange Services.
If your firewall is properly configured and only accepting email from Postini then I'm not sure why you would receive an email directly from anything BigFish.
What IP addresses are you allowing to relay into your exchange server?
Is it more then IP space that belongs to Postini?
If your firewall and mail servers are properly configured you should not be receiving email from anything 204.x.x.x