We are planning to deploy Exchange 2007 in our environment and need some help with where to locate the different servers and roles. I would like to be able to use OWA and Outlook Anywhere from the outside along with your normal Outlook use internally along with some OWA internally.I have 3 servers to be used for this install. What servers with what roles would I place on the DMZ andwhat servers with what roles would I place internally. Also which ones of these servers/roles need to be joined to the domain. I know this is asking a lot but I have done a ton of research and cannot find the info I need. Thanks in advance.

Ok, the deciding factor here would be what roles do you want to install on your network and what Server Licenses and CAL's you have. The Edge Transport Server should not be a domain member and is the only server which should be placed on the perimeter network (DMZ). All other server roles should be placed inside your network and where possible published using ISA or NAT rules on you firewall. Considering the number of servers you have, I would either combine the HUB and CAS roles into a single server or the Mailbox and HUB roles onto a single server. This depends on the transport rules and content protection you plan on implementing. If you wish to implement the max levels of protection then you have the option of scanning your comms at 3 differend stages on your network with a combination of Anti-Virus, Anti-Spam, Anti-Phishing and IMF's. The beginning would be at the Edge Transport server, IMF, A-V, A-S, A-Pon the DMZ, then again at the HUB Transport for AV and Routing Policies, when mail is being routed between mailboxes& Networks and finally at the Mailbox Server level where standard mailbox scanning is implemented. In this scenario I think it would be wise to deploy an Edge Transport SMTP Gateway, HUB/CAS combo, Stand alone MBX. Since the CAS server is used to publish all the "web enabled" services, which are accessible directly from the internet, I would always opt to keep this role seperate to my MBX server. Arguably, it makes perfect sense to combine the MBX and Hub Roles too since without the HUB the MBX is useless, i.e. mail will not transfer internally or externally an having them reside on the same box would negate any network connectivity problems between two physical servers. Bottom line - assess your current infrastructure & requirements, possible network growth and required scalability then decide from there which scenario suits you best.