We currently have a 2007/2003 mixed Exchange system in a hub and spoke environment. HQ=hub, and we have Site1, Site2, Site3. HQ is in 2003, all regional Sites are in 2007.
Each site has a seperate CAS, HT and MBX server. The regional sites are in the Exchange 2007 routing group, HQ is in Routing Group1.
Each HT has a RGC to Routing Group1 of cost 20.
I notice that if I change the cost of Site1's HT>Routing Group 1 connector to 10, then *ALL* mails to HQ are sent via this connector, regardless of which site's MBX server they originate from.
So, my question is, in a mixed mode environment, does Exchange 2007 use AD site link costs, or routing group costs (where the cost to other HT's in the Exchange 2007 Routing group is 0)?