BIS & other EWS applications in Exchange 2007 to 2010 coexistence

I have received comments about my "Installing your first Exchange 2010 CAS" 3 parts - tutorial that it didn't include any reference to services other than OWA. The reason behind this is simply because other services like ActiveSync, POP3, IMAP4, will work through proxying without the need for any additional configuration other than what has already been covered.

However I have faced a strange issue with Exchange Web Services and coexistence of Exchange 2007 and 2010. Since it is clearly stated on technet that

Clients that use Exchange ActiveSync, Exchange Web Services, POP3, and IMAP4 can't use redirection.

I thought it is safe to assume that EWS traffic will be proxied just like it is the case of ActiveSync, POP3 and IMAP4. My thoughts were further confirmed by the same technet article stating that Proxying supported between Client Access servers in the same Active Directory Site for the Exchange Web Services protocol (check section "Client Access protocols for redirection and proxying"), but obviously my thoughts were wrong!

Doing some tests with requests hitting the Exchange 2010 CAS server & using the famous test exchange connectivity website showed failures for users who's mailboxes are still on Exchange 2007 with the following error, while the test passed for users who's mailboxes are now on Exchange 2010.

The Client Access server version doesn't match the Mailbox server version of the resource that was being accessed. To determine the correct URL to use to access the resource, use Autodiscover with the address of the resource.

So it seems that the only way for EWS to work in a mixed Exchange 2007-2010 environment is that the application itself should support Autodiscover.

This is bad news, it means that my client will need to edit manually the settings for all its Blackberry Internet Service (BIS) users!

At this point I am still unsure if it is a bug but it looks like one, so if someone has more insight about it I would really appreciate the feedback.

About Antoine Khater

I have been working in IT consultancy and solution integration since 1998 and I consider myself lucky to be, one in a few, making a living out of my passion. I am also member of the famous Experts Exchange (profile here) online community where I try my best to share what I have learned along the road.