When I bought my Window Phone, one year ago, there was the first version of the operating system, so I easily configured (with advanced settings) my company’s exchange mail account on my phone.
In the last month, two colleagues of mine have bought Windows Phone with Mango yet installed on it, and for some unknown reason, the same procedure I made to configure my phone doesn’t work at all, on both devices.
The problem is that device says that there is not a valid certificate, and seems impossible to understand why it doesn’t retrieve the certificate.
So firstly tried searching on the web for the solution, and at the end, after a lot of different tries, I got the right one.
Of course I cannot assure the solution that has worked for me may fit your issue, but it is the following, make a try.
First, navigate with IE (or another web browser) to your “owa” web page (i.e. https://owa.mydomain.com/) and log into your webmail.
So click on the “lock” icon (or similar) into the url field to view and manage the certificate.
So this is the most important action (in my case): export (or save) the certificate on your file system using .p7b extension (that is the PKCS#7 version).
Then send this certificate in attachhment to another email account you are able to receive on the phone (Gmail or Hotmail). Download and install the certificate on the phone.
Then return on your settings and try to sync the Exchange account you have. In my case worked on both devices.
Now my colleagues can receive company’s mail. But I’m not sure they are happy about this… 🙂