In Exchange 2007, the Client Access Server (CAS) role accepts connections from clients in order to allow them access to the Exchange Server infrastructure (mailboxes, public folders, GAL, etc). CAS accepts connections from:
- POP3 and/or IMAP4 clients
- Outlook Web Access (OWA) and/or OWA Light clients
- Exchange ActiveSync (EAS) clients
Entourage falls into this category, and so when you are deploying Exchange 2007 alongside Entourage you will point your clients at your host running CAS. This is a change from previous versions, where you could enable IIS on any host and point clients there; however, it is similar in that CAS is very similar to the front end functionality that this option entailed.
There are certain design considerations CAS imposes, as well as benefits to how things were handled in Exchange 2003. With Microsoft Outlook clients, you could migrate a mailbox between Exchange Servers and Outlook would read the new location of the mailbox automatically and reconfigure itself for the new server. This has never been a feature of Entourage (although you can use a clustered pair), but now you point all clients to your CAS host and the mailboxes can then be moved between Storage Groups and Servers without having to touch the clients. However, if you change CAS servers you may find yourself performing some client reconfiguration.
In smaller environments, where ports are directly coming into the server from the WAN, you won’t find the CAS role to be a big design consideration. Clients can simply connect over port 80 or 443 (not including the LDAP lookups obviously). But in larger environments where all data needs to be proxied in some way, you may find the move to a CAS role complicated. Here, look to Microsoft’s IAS server, which would be placed into the DMZ and then allow connections from Entourage and other ActiveSync/OWA clients.
A number of people have been asking about ActiveSync clients, for Snow Leopard. The same principles will apply for Mail.app, provided it is a true ActiveSync client: simply point Mail.app at your CAS host.
One of the key reasons why Exchange adoption is so prolific is Public folders. Public folders are likely on their way out, giving way to replacing the concept with Microsoft SharePoint. I’m not going to say I love nor hate the idea, but in many institutions Public folders have been around for a long time, and while you likely will have until 2016 (worse case) to retire them, sometimes it takes as long to retire something as it took to build it in the first place… In the meantime, many of the common tasks for managing Public folders are going to require you to hop into PowerShell, so keep that PowerShell book close at hand if you find you’re doing a lot of work with Public folder management (New-PublicFolder -name BillyBob). Just something to keep in mind.
Finally, Exchange 2007 has a number of features for automatic archiving of data. Entourage has no features for auto-archive. So consider leveraging Exchange’s built in features, or as we’ve seen in some environments, having an out-of-band solution for managing archiving of mail to pst (or whatever format you prefer).