Unfortunately this workaround does not seem to work for me
I have three calendars in the device; "birthdays", "personal" and "calendar", of which the last one is the one I sync with davmail to an enterprise exchange calender. I am running PR1.3 with open kernel on the device.

The funny thing here is that when I first created the synchronization, it worked flawlessly for some time, then I noticed it did not update new appointments any more in the device.

Yesterday I got fed up with it, removed the "/home/user/.calendar/" directory and started over from scratch. Sad thing is, now I cannot get it to update even a single thing from davmail.
Looking at the /var/log/davmail during synchronization, however proves that it does authenticate correctly to exchange, and is receiving masses of html data.