The problem was the datatbase backup file as advised by Maemo Bugzilla Bug 11475
https://bugs.maemo.org/show_bug.cgi?id=11475

1. Delete /home/user/.activesync directory. I suppose, because of error 1) you
may need root privileges to do that. It can be done from x-terminal with the
command:
rm -r /home/user/.activesync

2. Delete activesync database. The first sync after reboot will take everything
from Exchange server again. Close email application before it. It can be done
from x-terminal application with the command:
rm -r /home/user/.qmf

3. Reboot the device.
4. Start sync if it doesn't start automatically. It can take quite a long time.
5. After the sync has been completed, run email application. If you don't see
folders, close and open it once again. It will re-read them from database.
6. Don't use that backup any more. It would be better to create a new one after
the sync has been completed.