Why is my ONID (Google) mail account not work after upgrading to Mac OS 10.9 (Mavericks) on Mac Mail?
After the upgrade to the latest version of Mac OS, 10.9 or Mavericks, Gmail users have started experiencing issues with Mac Mail and its compatability with Gmail. There is a wide range of items as symptoms, and some more severe than others. Apple has several forums about this issue, but there is currently no timeline for any approved solutions.
Apple has released a software patch to mac mail which addressess the issues. Please use Software Update to download and install the latest version of mac mail. More information on the software update can be found at http://support.apple.com/kb/HT6030