Why are Add-ons, and iCal and iPhoto integrations not supported for versions of Postbox purchased through the Mac App Store?
Apple requires that applications be self-contained, single application installation bundles that do not install code or resources in other locations. As such, we cannot support add-ons, iCal or iPhoto integrations for versions of Postbox sold and updated through the Mac App Store. We’re currently working with Apple to determine if there are any possible work-arounds to these restrictions. If we do find a work-around, or if Apple revises their guidelines, we’ll be sure to submit a new version with this functionality to the Mac App Store.