guys, I have the following: -One front-end doing OWA and ActiveSync. Sits in DMZ -One back-end. Sits internally -40 users with db size of 80-100GB What is the best and proper way to perform upgrade? Im concern about the new roles 2010 brings. I need exact steps including AD stuff.

Start with these links: Pre-Deplyment analyzer (to verify that your environment is ready for 2010): http://www.microsoft.com/downloads/en/details.aspx?FamilyID=88b304e7-9912-4cb0-8ead-7479dab1abf2&displaylang=en Then use the Deployment Assistant (to give you high level checklist of the install and configuration): http://technet.microsoft.com/en-us/exdeploy2010/default.aspx#Home Understanding Upgrade from 2003 to 2010: http://technet.microsoft.com/en-us/library/ff805040.aspx You might also want to check out some of the links on this page: http://howdouc.blogspot.com/p/exchange-references.html Tim Harrington | MVP: Exchange | MCITP: EMA 2007/2010, MCITP: Server 2008, MCTS: OCS | Blog: http://HowDoUC.blogspot.com | Twitter: @twharrington

And when it comes to the actual transition you can use the following guide http://msexchangegeek.com/2010/01/30/rapid-transition-guide-from-exchange-2003-to-exchange-2010/Jonas Andersson | Microsoft Community Contributor Award 2011 | MCITP: EMA 2007/2010 | Blog: http://www.testlabs.se/blog | Follow me on twitter: jonand82

Thank you for the info. Now for some quick answers, do I replace my front-end server with a server with only the CAS role? What is your take on that? My concern is that because the documentation is saying that "every" client MUST go thru a CAS server to reach a mailbox, then I "might" be forced to deploy 2 CAS servers? one to replace my front-end sitting at the DMZ wihch is only doing OWA and ActiveSync, and a second CAS server in the internal network so ALL my internal users can go to it to reach their mailboxes? what is your suggestion? thank you one more time

During coexistence you will need to keep your exch 2003 FE server up. As far as placement for the CAS....the CAS is not supported in the DMZ. It must be located in your internal network with the rest of Exchange and the clients. You can either punch a 443 hole from the internet to the CAS or take the recommended approach and publish your CAS with a reverse proxy server in your DMZ (like TMG). You do not need more than one CAS for 40 users. a single CAS can handle thousands of users. The only reason why you would want more if for high availability. In this case you would need load balancing (hardware or software).Tim Harrington | MVP: Exchange | MCITP: EMA 2007/2010, MCITP: Server 2008, MCTS: OCS | Blog: http://HowDoUC.blogspot.com | Twitter: @twharrington