As suggested at
Bug 30538 – VersaMail 3.5.4 does not sync mails there exists a way to backport the mobile sync features of 5.0.9 to 5.0.8. Obviously Zimbra doesn't want to be in the business of backporting, but they happened to have produced it already for another customer before 5.0.9 was released. If you are in the same sort of start-of-school-year situation as we are, you can ask support nicely for the existing zimbrasync.jar hot patch to apply to 5.0.8.