Except, of course, if your computer is not really your computer, be it only for a while. On any machine you share, it's good to have Gmail available offline, but it's even better to delete all cached data when you're done.
If you do not removed data, the next person using the computer can peek at all offline emails and attachments.
Delete the Offline Gmail Cache Data (Messages and Attachments) from Your Computer
To disable offline Gmail access in your browser and delete the cached data (messages, attachments) from your computer:
- Move the mouse over the Gmail offline icon in the Gmail status bar.
- Click Show Actions if present.
- Now click Disable Offline Gmail.
- Click Remove.