Google have released a beta version of Offline Google Mail, this is free app and it can be found on the Chrome Web Store. The app has a simple look, which is good and once downloaded it will synchronize email messages so the user is able to check their even if there is no internet connection available.
According to the web page at the Google Chrome Web Store;
Gmail Offline beta is a Gmail app built to support offline access, allowing mail to be read, responded to, searched and archived without network access. After first start-up, Gmail Offline will automatically synchronize messages and queued actions anytime Chrome is running and an Internet connection is available. More than just an offline app, the streamlined user interface, based off Gmail’s popular tablet interface, provides extremely fast response time with a pure, email focused experience.