There are many reasons why you see this error. But last week I learned something new. I had a client, which showed this error in the Configuration Information and also this pop-up
At the same time the MAPI Information was shown with MAPI Status OK. As long as Outlook was running the user had all features, because the client was using the Outlook integration via UcMapi.exe.
First I checked the client for the correct internal and external EWS URLs and that those could be reached succesful.
I also tried this KB article, even the mentioned cause did not match my scenario, without success.
Resolution
In the end I was able to solve the issue with the following steps:
- complete exit the Lync/SfB client
- locate and delete the file:
%localappdata%\Microsoft\Office\15.0\Lync\sip_<SIP address>\EwsFolder<SIP address>.cache
- restart the Lync/SfB client
Conclusion
I don’t know when this exactly happens, but I’ve seen this issue now several times and could solve it by deleting the EWSFolder cache file. But keep in mind that this is not a general solution. Hopefully this helps some of you.
The clueless guy 