To access Gmail even when you are away from an internet connection in your device you need to install the chrome app for offline Gmail access.
Once you install the application you will be able to access the mails in your inbox,can send mail,search and archive.Once you are connected to internet all the changes you made will be synchronized.
Steps to Install Offline Gmail
1. Goto Chrome web store page and install the application
2.The offline mode will be run in background
This application uses the HTML5 offline storage technology to store the emails for offline access.
Not just Gmail you can access Google docs,calendar in offline mode using this application.