First, the Log of which I am speaking is the Notes Log. Take a look at the Miscellaneous Events, as that view should show issues with connectivity. Mail routing issues are found in the Mail Routing Events view.
For mail to route from the hub to the primary server, do you have/need a Connection Document between the two servers?
If connections are bring refused from your Notes client and/or the other server to the hub server, those will appear in the Miscellaneous Events view in the Notes Log on the hub server.
I hope that this helps.
Feedback response number WEBB8V3L8Y created by Gregg Eldred on 06/08/2012