You don’t need to be online to access Gmail. Even if you’re offline without internet connection, you can open your web browser, go to gmail.com, and check your email just like you’re used to. Gmail uses Gears technology to download a local cache of your mail. When you lose your internet connection, Gmail automatically switches to offline mode.
You can read messages, star and label them, and do all of the things you’re used to doing while reading your webmail online. Any messages you send while offline will be placed in your outbox and automatically sent the next time Gmail detects a connection.
Here is How to setup offline gmail
Step 1: Install Google Gears
Gears is available for Windows, Windows Mobile (IE Mobile, Opera Mobile), Mac (Firefox, Safari), Linux and Android. If you are using Google Chrome browser, it has inbuilt Google Gears support, so no need to install.
Step 2 : Enable offline access
Click the Settings link in Gmail ==> Go to the Labs tab ==> Select “Enable” radio button for Offline ==> go down till end of the page and click “Save Changes“. Now offline is enabled
Step 3 : Install offline access to Gmail
(Now you will see link “Offline” near to settings on the top navigation bar )Click the Offline link ==> Click next ==> Check “I trust this site” and “Click Allow” button ==> Click Yes (to create a Gmail shortcut on your desktop for easy access )
Now, Gmail will do the initial synchronization with Gears, Please wait, this may take a few moments…
I tested it.. Looks cool..give it a try