Issue in sending mail from one secondary server to another

We have lotus domino 6.0 server as our hub server and six spoke servers connectiong through notes direct dial-up.Mail routing between the hub server and each spoke server is working properly.

The only concern we have is the mail routing does not work between spoke server to spoke server.For example if I have two spoke servers as server A and server C and if my hub server is server B , mail does not route from server A to server C via

server B.Mails addressed to server C from server A is not coming to server B either.However Mail adressed to a internet domain from a spoke server comes into the hub server and goes out to the recipiant.

We cannot dial into each spoke server from the hub server because the line is shared for both data and fax.What the spoke servers do is,they dial into hub server and pull all the mails that belongs to them.

I have created pull-push connection from each spoke server to the hub server.And no other connections are there.

Please let me know where I have made the mistake.