I am surprised that MfE even works for you on the N900 at all. The last time I used it, it synced only once a day, after my commute to work, when it switched from the mobile network to the company WiFi. Which was kind of useless: I did not need my work emails on my personal phone in the office!

(Mind you, the Exchange support in Sailfish is even worse. My last successful sync was weeks, if not months ago. I gave up and removed Exchange altogether. How can something supposedly actively maintained be worse than something abandoned years ago is beyond me.)