Gmail Offline is a Chrome Web Store app that's intended for situations when you need to read, respond to, organise and archive email without an internet connection.
This HTML5-powered app is based on the Gmail web app for tablets, which was built to function with or without web access. After you install the Gmail offline app from the Chrome Web Store, you can continue using Gmail when you lose your connection by clicking the Gmail Offline icon on Chrome's "new tab" page.
Google said on its blog, "The great thing about web apps is that you can access all of your information on the go, and we've introduced ways to use Google Apps on a variety of devices like mobile phones and tablets. But it's inevitable that you'll occasionally find yourself in situations when you don't have an internet connection, like planes, trains and carpools.
"When we announced Chromebooks at Google I/O 2011, we talked about bringing offline access to our web apps, and now we're taking our first steps in that direction. Gmail offline will be available today, and offline for Google Calendar and Google Docs will be rolling out over the next week, starting today."
Google Calendar and Google Docs lets users transition between on and offline modes. When you're offline in Google Calendar, you can view events from your calendars and RSVP to appointments. With Google Docs you can view documents and spreadsheets when you don't have a connection.
Offline editing isn't ready yet, but Google is working on getting it to users. To get started using Google Calendar or Google Docs offline, you need to click the gear icon at the top right corner of the web app and select the option for offline access.
You can download it from here. Offline Google Mail