iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple Releases Mail Update for Mavericks to Address Gmail Issues
Mail Update for Mavericks includes improvements to general stability and compatibility with Gmail, including the following:Full information on the update, including Apple's recommendations about backing up before applying the update, are included in an Apple support document. The update is available via the Software Update mechanism in the Mac App Store.
- Fixes an issue that prevents deleting, moving, and archiving messages for users with custom Gmail settings
- Addresses an issue that may cause unread counts to be inaccurate
- Includes additional fixes that improve the compatibility and stability of Mail