At my company we have two AD sites, and I have configured our Exchange 2003 routing topology to mimic this setup. We have also two non-exchange SMTP gateway servers at each site, that all outgoing email flows out of. Our current setup is we have SMTP connectors in each routing group, that have an address space of * and a cost of 5, that route all mail through their respective gateway servers, in their site.
To create a redundant enviornment, I have also created another SMTP connector in each routing group, with a cost of 7, that routes email from Site A, out through the gateway server in site B, in case of a server failure in Site A, or loss of internet connection. This allows outgoing email to automatically start flowing out to remote site, so that there is virtually no downtime for outgoing emails. This works great for us.
I have begun designing our Exchange 2007 migration, and in my tests, it seems that the same setup with multiple send connectors does not work in Exchange 2007. From reading Microsofts documentation, it seems that this is by design. Exchange 2007 does not use link status updates, so it will not re-calculate a route if a server is down, so essentially admin interference is neccessary. I know that I can create a send connector, and specify both of the gateway servers as smart hosts, and this will work, but I also dont want this to be used in a round robin approach.
What is the best way, and what have you guys used, to create the above enviornment in Exchange 2007. Essentially each site will have one hub transport and one mailbox role installed. Each site will have its own dedicated non-exchange smtp gateway server. If the gateway server in site A fails, how do i get email to route out through the gateway server in site B, besides adding this as a second smart host in the send connector?
Sorry for the lenghty post.