hi together,
unfortunately i have the same problem
"Either Exchange server requires secure connection or account is disabled"

our company has exchange server 2007 - allow non-provisionalble devices is enabled.

I got two different certificates and tried to install both of them.

First is from other nokia devices and installation on N900 was no problem but I have still the same error message!

The second certificate is from our website! I'm not able to install ths second certificate on the N900!
I exported it with all possible endings (.crt, .cer, .p7b) and saved them on my N900. When trying to install them there is no "install" button on my n900 as it was before!
When clicking on the certificate just the details have been shown but no possibility to install it!

certificate is also not in the certificate manager!!

would be great to get support!!