Update on Wildcard certificates

Not that long ago I talked about using wildcard certificates to allow you to move OWA and ActiveSync services from one physical server to another.  Since single certificates are assigned to a single server, failing over or moving to another server would cause the clients to suddenly lose SSL connectivity, as the certificate would not match up, and ActiveSync devices cannot pop up the error about a non-secure connection. OWA can, but it can be troublesome with end-users who suddenly start seeing security warnings.

Following up on this theory of using a domain-assigned wildcard certificate, research has shown that older Windows Mobile devices (WM 5 or earlier) cannot leverage these types of certificates at all.  WM 6 and higher can leverage this technology, but earlier versions were not coded with the required information to recognize that a certificate could possibly be assigned to more than one physical server or networked device.

So, for those using WM 6, OWA and Outlook Anywhere, you can use wildcard certificates to allow for services to move from server to server as required.  For those using earlier versions of WM (or the 3G iPhone - though the jury is still out on that one), you must use server-specific certificates, and re-configure the devices' ActiveSync connection if the server itself moves. 

None of this impacts Blackberries, as they authenticate via the RIM network, and not directly to the Exchange servers.  If you're using Blackberries, wildcard certificates offer the ability for all other mobile systems (OWA, Outlook Anywhere, etc) to move with your servers in the event of a loss of a particular physical machine, while RIM will handle moving the Blackberry devices.

Long story short, if you're on WM 5 or earlier, be ready for a few support calls when you need to move the services or fail over between servers - even if you use wildcard certificates.  If your users are on the new iPhone systems, be sure to keep a close watch on Apple's forums, as new information is being discovered every day.