Question : Seting up routing connectors in exchange 2003

Hi, I'm running Exchange 2003 SP2 Server 2003 R2.

My current seup is:
Site A
Server 1: Spam server
Server 2: Front End HTTPS RPC
Server 3: Back End Master Server

Site B
Server 4: Back End Master Server

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Inbound and Outbound emails go through Server1. Server 1 delivers inbound externa mails to server3.

I need to get Server 3 to forward the emails to Server 4.

Can anyone advise me what routing connectors i need to set up between site A and Site B?
I have already set up SMTP connectors on both sites to forward all mail to server 1.

Currently Site A can send/ Recieve external emails, but not internal mails to site B. Site B can send external and Send/ Recieve internal within its own site, but cant recieve any emails from site A (External emails and  Site A Internal.

I have also check DNS which looks fine.

So as it stands, i have a routing group connector with an increasing queue on Server 3. Can anyone advise what to do?

Many Thanks in advance

Answer : Seting up routing connectors in exchange 2003

Create an SMTP Connector on Server 3:

http://www.msexchange.org/tutorials/Configuring-SMTP-Connector.html