Click Save Changes and you're done. The new feature allowed Gmail users to work without the internet connection and save all the changes once Gmail is connected to the internet.
This new functionality, which I found out about thanks to 9to5Google-I don't believe there's an official announcement-marks the first time that Gmail has natively support offline usage. The new in-built offline feature is certainly an upgrade and is a boon for users who would like to stay productive even in areas where they expect to be limited or no connectivity.
Click on the gear icon below your user portrait. When users choose to keep it, the data will not be deleted from the computer once they sign out of their Google account.
On the Offline menu click Enable Offline Mail and you'll see a screen with several options on it (Figure C).
It's possible to send e-mails while in offline mode, but these messages will be stored in the Outbox folder until a network is available, at which point it will promptly get sent. If left behind, cached emails could be a serious security risk.
If that sounds ghastly, then you can turn them off (they're on by default) but then we weren't sure about snoozing emails and that seems to be working out rather well, so perhaps give it a chance?
Go to your Gmail settings and choose the "Enable experimental access" feature on.
Before you go all-in on offline mode, there are a few limitations you should know about.
Offline mode is only available for people using Chrome, so if that isn't now your browser of choice, you'll need to download it for starters.
Under "All cookies and site data", click Remove all. Usually, this is only a fraction of the storage available on your computer, so the available storage shown in Gmail offline settings is smaller than the actual available storage on your computer.