I'm getting a rejected email from a specific domain only, the rejection message is: "451 4.1.8 Possibly forged hostname for 220.127.116.11 (in reply to RCPT TO command)".
I have only one exchanged server 2010 and barracuda at front. I have setup sendconnectors that the smarthost point to barracuda as a smarthost, under sendconnector network properties.
Domain records are at Register.com. 18.104.22.168 resolves to barracuda.trendsinternational.com and reverse records also resolves to barracuda.trendsinternational.com.
Again, there is only one customer rejecting, our emails.
thank you very much!