I will lay out the configuration and then my questions.
Let's say I have two Active Directory sites, site A and Site B. I have two Exchange 2010 HT servers in each site for a total of 4 HT enterprise wide. As I understand it, the Microsoft Exchange Mail Submission service on mailbox servers automatically load balances connections among the HT servers within a site. Thus my questions relate to when failures occur.
If a HT server fails in Site A, will the mailbox servers simply use the second HT server in Site A? Logically it will, but just checking.
If both HT servers in Site A fail, will the mailbox servers cross to Site B and automatically begin connecting to the HT servers in Site B? I ask this question as I see references: “Hub Transport server to Hub Transport server communication inside an organization automatically load balances between available Hub Transport servers in the target Active Directory site.” What I do not see is anything answering what happens when the local HT servers both fail.
For external mail delivery (mail coming from the outside), can I and should I use a load balancer to pass mail to any of these HT for HA? Are there any issues to using say a Foundry to LB among HTs or should I just have my Smart Host point to all HTs? Any ideas would be appreciated. Thanks all.