Google's email service, Gmail, ran out of juice on Tuesday afternoon, leaving many users with no access to their email, online calendar or contact information.

Even the official mail system used by the Google India staff crashed because of system failure. Google applications like search, blogger, blog search and Google news, however, remained unaffected.

"Many of our users had difficulty accessing Gmail today. The problem is now resolved and users have had access restored. We know how important Gmail is to our users, so we take issues like this very seriously, and we apologise for the inconvenience," a Google India spokesperson said.

The Gmail problem was flagged up immediately on Twitter, an online microblogging site, with many users saying that they had IMAP access running as normal.

"Essentially, anyone running Gmail through IMAP on a desktop email client or through their iPhone may well be fine," explained the Google executive.

Thousands of Twitter followers expressed their displeasure on Twitter. One Gmail user wrote on Twitter, "Seriously Gmail, I had some things to do this morning with you. You let me down. Hard." Others talked of having to revert back to Lotus notes and other email accounts.

Microsoft officials did not fail to cash upon the opportunity to poach a few users from Google, its arch-rival "Need a new email account? Take a look at windowslive.co.uk - awesome," twittered Mel Carson, Microsoft's advertising community blogger.

The outage exposed the underlying vulnerability of 'cloud' computing, in which applications and data are accessed by users on the internet instead of their own hard drives. Google has been trying to sell its cloud-based Google Apps service to businesses for a couple of years, with notable success in getting some companies to switch to Gmail from Microsoft's Outlook.