I recentley had to add an exchange 2010 server into a 2003 organization. As part of the installation a routing group connector is created but for some reason it was not created correctly created. Here is how to create a routing group connector in powershell from exchange 2003 to exchange 2010
So first run the exchange 2010 power shell . Once you are in the exchange powershell copy and paste the command below making changes the the server names.
New-RoutingGroupConnector -Name "RGC 2003-2010" -SourceTransportServers "exchange2010server.yourdomain.local" -TargetTransportServers "exchange2003server.yourdomain.local" -Cost 100 -Bidirectional $true
Ok so replace exchange2010server.yourdomain.local with the FQDN of your exchange2010 server and also replace exchange2003server.yourdomain.local with the FQDN of your exchange 2003 server.
Then on the 2003 server, restart the smtp service and then on the exchange 2010 server restart your exchange transport service.
The connector is bi-directional so mail will now flow both ways.
To view the routing group connector enter
For more powershell commands view our powershell commands guide