I am also having issues with MFE on the n900
We are using exchange 07
I am part of the IT department
It works over Wifi, but if i use TMO internet it does not.
I installed the cert from our OWA web portal, and now i can actually see the web page for the web portal, but MFE does not work over tmobile internet at all. I can only sync via wifi. I tried hte finnish trick with no avail Anyone have any ideas or a way i can resolve this problem?
I was also on the line with TMO tier 3 support with no luck, they said my line has no internet blockings and such, so i am totally lost as to why its not working? Any help would be appreciated
I also checked the non provision device trick, and we allow non-prov devices, so i am not sure what hte problem is....anyone else in my boat or knows how to fix my problem?

Update: Have a Tmo engineer looking into it....As i was guessing, its a tmo problem.