If you are a Google Mail user who is using the Gmail website to read emails, you know that you need a working Internet connection to access the emails. If you are not connected to the Internet, you cannot access your Gmail emails. There are options to work around this restriction, use a desktop email client for instance in addition to the online client, or use the Offline Google Mail extension for the Chrome browser.
Offline Google Mail is an official extension, created by Google for users who want to have offline access to their mails. You can install the app at the official Chrome Web Store. Since it is an app, you need to log in first before you can do so.
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.
When you launch the app for the first time afterwards, for instance by opening a new blank tab in the browser and selecting Offline Google Mail from the apps tab, you need to explicitly allow offline mail on the computer Chrome is running on.
It is not suggested to allow offline email access if you are on a public or shared computer, as other users may be able to read your emails this way.
Gmail emails will automatically synchronized with local storage from the moment you activate the extension and access the Gmail website. Keep in mind that it may take some time before all messages have been synchronized. You can read synchronized emails, and reply to messages as well. These replies are then queued locally until an Internet connection is available again.
Offline Google Mail can be useful for Gmail users who sometimes do not have an Internet connection at their disposal but need access to their messages all the time. The option to reply to messages while offline could prove to be very handy for those users. (via Blogtechnica)
Chrome users can stop the synchronization any time in the following way:Type chrome://settings/cookies into your address bar and press enterSearch for mail.google.comHover over the search results and click the X that appears
This stops the synchronization but not the data that has been stored on the computer.