Exchange 2010 SP2 RU1 and CAS-to-CAS Proxy Incompatibility

OK, I’ve finally got it. While testing e2010 SP2RU0 to e2010 SP1RU6 OWA proxying scenario, and getting the same error about the proxying failure, I noticed the additional event in the Application log (see at the end of the post) which tells us that we need to copy OWA folder with the older OWA code to the proxying server. That was something new for me. And after that the proxying issue to an older OWA version was resolved. But this technic does not work for SP2RU1 and while trying to proxy I’m getting the error explained in this Exchange Team’s blog post.

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Log Name:      Application

Source:        MSExchange OWA

Date:          2/21/2012 7:28:59 AM

Event ID:      46

Task Category: Proxy

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      EXCAS1.qwerty.qwerty

Description:

Client Access server "https://excas1/owa", running Exchange version "14.2.247.5",  is proxying Outlook Web App traffic to Client Access server "exhcm.qwerty.qwerty", which runs Exchange version "14.1.355.2". To ensure reliable interoperability, the proxying Client Access server needs to be running a newer version of Exchange than the Client Access server it is proxying to. If the proxying Client Access server is running a newer version of Exchange than the Client Access server it is proxying to, the proxying Client Access server needs to have an Outlook Web App resource folder (for example, "<Exchange Server installation path>)ClientAccessowa8.0.498.0" that contains all the same versioned resource files as the Client Access server it is proxying to. If you will be running Outlook Web App proxying with mismatched server versions, you can manually copy this resource folder to the proxying Client Access server. After you copy this resource folder to the proxying Client Access server, you need to restart IIS before proxying will work.