I just acquired a new iMac after years of using Windows desktop computers. Pleased with the new machine, but I really miss a mail notification program called Pop Peeper that only runs on Windows (website: http://www.esumsoft.com/products/pop-peeper/ ). Herald for Mac looks like it could be an effective replacement. Does it work well in Yosemite? Do I really have to back up my whole computer before installing it? -- the following paragraph spooked me a little on a website that was reviewing it: Note: Mail plugins are not officially supported by Apple. While Herald has been thoroughly tested, it's possible it may cause unintended conflicts with Mail or with other unofficial Mail plugins, especially after OS updates. It's recommended that you backup your computer before installing Herald or any other Mail plugin, and always before installing any updates to Mail or OS X. Any info would be much appreciated!!