I have an existing Exchange 2007 install. One server has three roles, CAS / HUB / and Mailbox. We are transitioning to Exchange 2010. I have installed the 2010 CAS / HUB roles on one server and the mailbox role on another. I have not moved any mailboxes as of yet. Everything still resides on the 2007 server. Internally, OWA works fine. If I go to https://internalmail/owa, I am prompted with the yellow 2010 OWA login screen (yellow screen = 2010, blue screen = 2007). I can login just fine and my mailbox appears with no issues. Externally, if I go to https://externalmail/owa, I am prompted with a new ssl certificate prompt and if I acceept, I get the yellow 2010 OWA login screen. So far so good. However, when I login to OWA, I get a page cannot be loaded error and the error mentions that the host is responding in a way that will never get resolved. I did change the address translations in the firewall. So, before the switch to 2010, the externalmail ip address 1.2.3.4 was pointing to 10.1.1.45, which was the 2007 all in one server. After installing 2010, I pointed the externalmail ip address 1.2.3.4 to 10.1.1.46, which is the new 2010 CAS / HUB server. Essentially, the external ip address on the public side did not change and still has the same dns name, externalmail. Only the internal ip address changed. So to end users, they still type in the same address that they have always used. Final note is that if I use a new external ip address for externalmail, for example 1.2.3.5 and map it to the new CAS / HUB ip of 10.1.1.46, OWA works externally just fine. What steps have I missed that allows the existing externalmail ip address of 1.2.3.4 for OWA to work externally? I can't seem to find the solution and I have searched extensively for the answer. Thank you in advance.

You have made a common mistake and presumed that Exchange 2010 works in the same way as previous versions - that you can have users on both servers access OWA through the same server. Even I made that error when I first setup Exchange 2010. Unfortunately that is not the case. Exchange 2010 will not proxy the older versions of OWA. You need to have both Exchange 2010 and Exchange 2007 exposed to the Internet, with unique URLs and appropriate SSL certificates. Users on the old server will be redirected to the old server if that is where their mailbox is held. You will need to ensure the external URL is configured correctly on the Exchange 2007 server etc. Therefore to have a co-existence period you will need to have two external IP addresses and relevant host names, and the name of both external facing host addresses in the SSL certificate (allowing you to have one SSL certificate shared between both servers). Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Hi, You will have to confiure legacy name for the Exchange 2007 Internal url and you will have to disable External Url on Exchange 2007. Please refer to the below article's for more inforamtion on the upgradge path from Exchange 2007 to Exchange 2010. http://technet.microsoft.com/en-us/library/dd351133.aspx http://technet.microsoft.com/en-us/library/bb124350.aspx Thanks. Nagaraj N

Thanks. I was able to get it going by setting up the legacy.comapny.com dns entries, both internal and external.

Thank you kindly for the detailed information. I found this article: http://blogs.technet.com/b/sjimmie/archive/2010/07/09/owa-coexistence-with-legacy-versions.aspx which explains how to configure the "Proxy" portion of the coexistence. Do you perhaps know if such configurations will work and is supported? If this solves the proxies for OWA, will this also work for Outlook Anywhere & other Remote Sync services such Blackberry Internet Services? Thanks in advance.