I have an Exchange 2010 (SBS) configuration set to accept emails to two domains. I am also using a postfix gateway server to perform spam and virus filtering. I have added a connector that allows the postfix server to properly relay messages into the exchange server, but for some reason this is only working for the primary domain created by the SBS install. The secondary domain will not allow messages from the postfix server. The secondary domain will properly receive messages when they are not relayed through the postfix server.
Further testing also shows that the secondary domain is rejecting messages from my store-and-forward server - which the primary domain has no trouble for.
The messages are all being rejected as 554 5.7.1 <[user]@[secondary domain]>: Relay access denied.
My "From NetGate" connector has the IP of the postfix server for the receive field, authentication has been tried with all, and with none, and with TLS and External - no difference.
permission groups have tried everything, no difference, currently set to anonymous and both exchange options.
I have even added the IP address for the postfix server to the IP Allow List in the anti-spam tab of the hub transport.