Nothing is truly permanent — especially on the Internet — so Google is working towards allowing users access to e-mails anytime, even long after the company's online services are gone. Google offers a one-click export system to download a copy of your data from Gmail and Google Calendar.
Previously, users had to turn to not-always-effective third party backup or extraction services. Now, Gmailers can download their entire archive of mail or select labels as an MBOX file. MBOX is a common format for storing email messages, with all of the user's email threads stored in a single, long text file. Many clients, such as Entourage, Eudora, and Mozilla Thunderbird, can recognize MBOX files.
To export your personal data, sign into your Google account, click on the profile thumbnail in the top right corner, and select "Account" just beneath your email address. In the navigation menu on the left, click "Download your data" and select "Create an archive" to begin picking and choosing the Google services you'd like to preserve.
Calendar export is available for all users today, and Gmail export is rolling out over the next month.