It took me a bit of time to come back to this issue because I stopped using N9's MfE client for syncing email - it was being just way too troublesome.

But I got my own N9 (was testing with wife's before) and now there is a new firmware, and I decided to test again. And I can categorically confirm (a) that it won't sync at all with the server - permanently seems to 'hang' with endless sync that syncs nothing, and no sync activity on server - and that it immediately works if I UNCHECK 'Non-provisionable device' - without rebooting the device or doing anything else. I can also categorically confirm that the server DOES NOT require provisioning - I know this because I use my N900 to sync email with the very same server, and the very same account, and the N900 of course does not support provisioning. Also, the server is nuevasync.com, and they explicitly say that provisioning is not required.

So I will repeat: on at least TWO 64GB N9s that I have tried, NEITHER will sync AT ALL when the device is set to non-provisioning with the service I use. And this has NOT been addressed with the latest firmware.

If you would like me to check logs, I am happy to do that, but I do not know where they are. And please note that David Boreman at Nuevasync.com knows about this issue and I am in active communication with him trying to troubleshoot the N9's syncing on their servers.