Today Google released new updates to the offline version of Gmail in their Chrome web browser. While offline support is nothing new for Gmail, you can no synchronize up to 31 days of mail for offline access. All attachments are also downloaded for easy access, along with full keyboard shortcut support and a variety of performance boosts. To give this new version a try, just install it via the Chrome Web Store.
Improvements to the Gmail offline Chrome app | Official Gmail Blog
