Troubleshooting mail delivery (Exchange 2010) - receiving from relay
I'll explain the complicated setup I have initially...
1. LancsNGfL mailserver accepts mail destined for our domain
2. The LancsNGfL mailserver then relays that mail to an IP address
3. The IP address mentioned in 2 is then nat-ed with a port forwarding rule to my Zimbra server
4. If the Zimbra server does not have the recipient, the mail is relayed onto my Exchange server
Now the problem...
I'm decommisioning the Zimbra server so there's now no accounts on it. My Exchange server is sat happily receiving mail.
If I change the port forwarding rule to point to the exchange server (which has a recipient rule on it accepting mail from thew LancsNGfL relay), I stop receiving mail. Changing the port forwarding rule back fixes the problem.
What am I missing? :confused: