After some digging I thought I’d try some of the EWS URLs manually in a web browser. I’d tried some of the others and although they produced odd things, they at least did something. The EWS URLs just produced a 404.

Looking in IIS there were clearly files in the EWS directory with the correct names, so something else must have been missing. I started a comparison with another reference system. Eventually I noticed a difference in the web.config file located in C:\Program Files\Microsoft\Exchange Server\ClientAccess\exchweb\ews.

The copy on our production system contained entries like this:

<codeBase version=”0.0.0.0″ href=”file:///%ExchangeInstallDir%bin\Microsoft.Exchange.Common.IL.dll” />

Whilst our reference system contained entries like this:

<codeBase version=”0.0.0.0″ href=”file:///C:\Program Files\Microsoft\Exchange Server\bin\Microsoft.Exchange.Common.IL.dll” />

As far as I could tell %ExchangeInstallDir% was not set on either system. Further, looking at the autodiscover and OWA web.config files I noticed they did it the same way as the reference system.

So I ducked over to a Unix system, did a proper comparison of the production file versus the reference one and determined that the only difference was the expansion of the variable. So I simply dropped the reference one in to place on the production system and restarted IIS.

And it worked!

I’m not sure how we got in to that state, but I’m pleased it’s sorted out. I’m not particularly getting on with this Exchange stuff, and peculiar issues like this really don’t help. Given we installed both the production and reference systems in the same way I can’t understand how this happened.

Now to fix the remaining issues…

Update: Now that I know what the issue was I can google for it. I found this post (better formatted here for non-IE users) which shows that the issue occured with the accidently released update for Exchange a while back. We got this update in the small window in which it was available and later uninstalled it. Looks like that caused the problem.

Related posts:

1. Upgrading Debian