Here’s the deal: The new operating system, Mavericks, has been showing to have a problem with the Mac Mail application. Specifically, if you have OX X Mail set up with Google Apple or Gmail, you may be having a Mac email issue. What is happening is the email and contacts syncing is not working properly and is buggy.
Until the Apple support team says there’s an email fix for Mavericks, do not upgrade to Mavericks.
If you don’t use Gmail or Google Apps for your Mac Mail program, then go full speed ahead and upgrade to Mavericks. After all, it’s free and fun to play with!