Microsoft has another great podcast up around the messaging design that went in to its Exchange 2007 environment. And please Microsoft, let me download the entire podcast so I can listen to it offline. IMO that is a requirement to be a podcast. Streaming sucks.
From the download page:
Ever wondered how a large enterprise plans and implements design and architecture of its next generation of messaging system? View this content to find out how engineers from the Microsoft IT messaging team will uncover the details on how Exchange 2007 infrastructure was introduced and fully deployed in a 120,000+ mailbox production environment. Topics will include: messaging topology design, hardware planning for various Exchange server roles, Client Access Server and Mobility scenarios, Transport architecture, Mailbox server and storage designs, backup, restore and high availability strategies.