Considering the following Scenario when receiving mail for Test.com :
Internet > Ironport1 > Internet > Ironport2 > Exchange.
An ironport from a sister company receives mail for Test.com. Then relays the mail over the internet to my Ironport and then my Ironport send it to my user in exchange.
Do I need to setup an Incoming Relay in my Ironport2 for this to work properly?