I’m still trying to get my head around Exchange 12 mail flow and message routing but I’m sure it’ll become clearer once we get the servers up in the other sites. I’m hampered a little by the fact that this beta doesn’t have a GUI for configuring the bridgehead servers so I can’t have a nose around the settings.
From my understanding so far Exchange 12 is an Active Directory site aware application so it is very important that your Subnets and IP Site Links are correctly defined in AD Sites and Services. After checking available hardware in the various regions I’ve settled on 4 AD sites in the sandpit environment. These are Crawley (UK), Tampa (US), Santos (Brazil) and Montreal (Canada). The sites will be fully meshed with IP Site Links. To begin with the links will have uniform costs but at a later stage I’ll be investigating whether adjusting the values has any impact on mail routing within our organisation.
For the Crawley site we’ll have 4 servers initially. There will be a domain controller containing the global catalog, a mailbox server, a server with the bridgehead and client access roles and a gateway server. According to the release notes the gateway server role hasn’t completed the security pass. Therefore we’ll keep it on the internal network and route email to/from it via a Mailsweeper server in our DMZ.
I’ve placed a diagram of the Crawley topology below. Click on it for a larger version.
I’ll provide more information once the other sites are running and we’ve had a chance to experiment with connectors and mail routing. There’s no point me regurgitating the help files at this stage when I don’t have a decent understanding.