Microsoft Windows Live Hotmail users who signed into their accounts on the evening of April 9 may have experienced a shock when they received a message that said, "You don't have an inbox ... yet."
According to Microsoft, an undisclosed number of users experienced a temporary outage "caused by a networking issue" that has since been resolved. User messages remained intact on Microsoft's server during the downtime, which reports said also affected some Xbox Live and Zune Marketplace users.
Hotmail services were completely resolved by 11:25 PDT. The outage had lasted roughly 2 hours.
In a posting on a corporate blog, the Windows Live team said the networking issue was "encountered while doing routine maintenance."
As cloud-based e-mail services such as Hotmail have attracted more and more users, outages can affect tens of millions of people. According to ComScore, Yahoo Mail had 91.9 million unique users in 2008, followed by AOL Mail with 46.6 million users (and another 7.2 million visitors to AIM Mail), Hotmail with 43.5 million and Gmail with 29.6 million.
For its part, Google has been working on transforming its Gmail service into a more robust and enterprise-ready messaging and collaboration tool, adding applications such as Google Calendar and chat features, and enabling offline use of Gmail. Microsoft, Yahoo Zimbra and other e-mail clients also offer offline access.
However, IT companies have wrestled with the challenge of providing as much uptime as possible to those users relying on their cloud-based messaging and collaboration services.
In February and March 2009, Google Gmail experienced some outages of a few hours' duration. While service was restored quickly to the bulk of users, after the February outage Google ended up offering 15 days of free service to those enterprise customers and others paying $50 per year for expanded versions of Gmail and Google Apps.