Our organization has about 25 Exchange 2003 servers (and no Exchange 2007 servers). We have quite a few Mac users that would like to use Outlook 2011 to connect to their Exchange 2003 server mailbox. It is well documented that this will not work directly since Outlook 2011 uses the Exchange Web Services protocol (EWS). However, it appears to me that I should be able to install a single Exchange 2007 server with only the CAS role installed. The Mac Outlook 2011 clients could then point to the CAS server and use EWS to access their 2003 mailbox (the CAS server should proxy the traffic to the correct ES). Does anyone know if this will work? Thanks...

That will not work.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Hi Ed, Thanks for the quick (and short) response. It would further my knowledge of ES2K7SP3 to have a reason. Is it because the EWS protocol is simply proxied to the server that holds the mailbox, meaning that the mailbox role on the applicable backend server must also be able to communicate via the EWS protocol (meaning it must be ES2K7+)? Thank you very much for sharing your knowledge. Dave Garner

Exchagne 2010 CAS redirects EWS to Exchange 2003, it does not proxy. The only thing that Exchange 2010 proxies for downlevel Exchange servers is ActiveSync.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Hi DR Garner, Sorry for the early mark! After do more research, if you just want to deploy the exchange 2007 cas server in the exchange 2003 scenario, and act as the FE for exchange 2003 server, it maybe achieved, althought I have not do such a test. In my opinion, when we do the upgrade for the exchange 2003 email system to exchange 2007, we will deploy the exchange 2007 CAS server role firstly. And the cas server role would also could proxy the activesync for the mailbox on the exchange 2003 server, please refer to below information: http://blogs.technet.com/b/exchange/archive/2007/01/05/3397655.aspx http://blogs.technet.com/b/exchange/archive/2007/10/12/3404136.aspx Regards! Gavin TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click “Mark as Answer” on the post that helps you, and to click“Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread

While you are correct that in an upgrade sceanario the proper procedure is to deploy the Exchange 2007 CAS role server first, the Exchange 2007 CAS does not provide much if any benefit to users whose mailboxes are on an Exchange 2003 mailbox server, and that was the question that was asked. Your links corroborate my answer, that the original proposition, that support for Mac Outlook 2011 could be provided simply by installing an Exchange 2007 CAS, will not work.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

I agree with Ed, EWS is just an API that to talk to Exchange but Exchange 2003 does not no of that API so adding a 07/2010 CAS is not gonna add 07/2010 features to a 2003 mailbox.DJ Grijalva | MCITP: EMA 2007/2010 SPA 2010 | www.persistentcerebro.com

Thanks all for the very informative answers. My original thought process was that the CAS role would convert the EWS protocol data stream to another protocol stream that E2003 would understand. From your explanation it appears that the EWS data stream simply passes through the CAS server to the appropriate E2007 server that holds the mailbox. If EWS traffic were passed to a E2003 server the operation would fail since E2003 does not underatand EWS. This is what I plan to setup so that my Mac Outlook 2011 users will be happy: - replace my existing E2003 FE server with a E2007 server with only the CAS role. Test (externally) OWA, ActiveSync and Outlook Anywhere to make sure all work as they did before. - install another E2007 server with the mailbox role. Move the mailboxes of my Mac users to this server Please let me know if you see any showstoppers with this deployment. I do intend to upgrade all E2003 server to 2007 but that is going to take time and a lot of planning. I need to do this as a quick fix for my Mac users. Also, another quick question: Can Mac Outlook 2011 use the Outlook Anywhere feature? If so I assume that the Internet-facing side of my CAS server will handle the EWS(?) traffic to the appropriate E2007 server without changing the url (only the CAS server IP will be mapped through the firewall for incoming http/https traffic). Thanks, Dave Garner

You don't want to replace the Exchange 2003 front-end servers, you'll still need them because the Exchange 2007 CAS servers redictect to them. Just add one or two CAS servers. You'll be able to remove the front-end servers after your Exchange 2003 users are moved to Exchange 2007. At this point, why aren't you installing Exchange 2010? Exchange 2007 is nearing end-of-life. Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Also, you could have both the CAS and MBX role on what should probably be a E2K10 server (E2K7 is already 4 years old - see previous post). That might save you some time and money (licensing). You do not need to reproduce the FE - BE distinction with E2K7 or (preferably) E2K10. All roles (besides the Edge, if present) should be in the internal network and could be on the same server. EDIT - besides applicable Technet articles, the book "Exchange 2010 Best Practices" has some useful information on managing mixed E2K3 and E2K10 environments, not to mention migration/transition.

HI DR Garner, ED and Le piver gave some good information. What I referred, just want to express that if there is just one CAS in the exchange 2003 scenario, it also could be work. But, I do not confirm it with ourlook 2011, because I have no the test lab. :) I also think it is better to install the exchange 2010 server, and after the deployment for exchange 2010 server roles, and then move the account who want to use the outlook 2011 to exchange 2010 mailbox server firstly, and then use the outlook 2011 on the MAC client. Regards! Gavin TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click “Mark as Answer” on the post that helps you, and to click“Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread