14 DAY TRIAL // Apple has released a brief note to developers who leverage the Mail component of OS X, informing them that Mavericks will break compatibility with apps that use temporary sandboxing entitlements for composing email.
According to a brief technical note posted on the News and Announcements section for Apple developers, “When OS X Mavericks becomes available later this fall, apps running on OS X Mountain Lion or later can no longer use temporary sandboxing entitlements for composing email with Apple Mail.”
Developers are told to update their apps to use Scripting Targets, and are directed to the Mac Developer Library for more information about “Adopting Scripting Targets for Composing Mail.”
There, Apple goes in-depth, telling programmers exactly what to do in what circumstances, i.e. “if your app composes messages in Apple Mail using AppleScript, and has a minimum OS of 10.8, and [etc., replace this code with this code].”