Exchange clustering and firewalls

Rod posts today about the strange (and sometimes frustrating) behavior where outbound SMTP connections from an Exchange cluster originate from the host IP address rather than from the virtualized IP resource associated with the Exchange Virtual Server. Great post and this is a common question on the newsgroups, etc.

Scott Landry also talked about the technical reasons behind this SMTP/network behavior in some detail (it has to do with networking APIs and OS routing tables) as “Myth 4” in his SMTP Virtual Server Myths post.