"could not sync mail accounts to the iphone because the iphone cancelled the sync"

I got this problem after adding a new mail account to my Mac and then trying to sync it to the iPhone (by selecting it to Sync in iTunes).

If you have a JailBroken iPhone, you can fix this by:

ssh root@xxx.xxx.xx.xxx (default password is 'alpine')
cd /var/mobile/Library
chmod -R 777 Mail/