Business and consumer users of Google's popular e-mail service were today hit by an outage. "Server Error. The server encountered a temporary error and could not complete your request. Please try again in 30 seconds," reads the message to users, who tried to access their mail. The service went offline at 0930 GMT with Google saying it was "working hard to resolve this problem".

Professional users of Google mail are covered by a service level agreement that promises to be 99.9-per cent operational in any calendar month. More than 113 million people use Google mail worldwide, according to comScore.

Google has the world's third most popular web mail service behind Hotmail with 283 million users and Yahoo with 274 million e-mail users.

In a statement, Google said "a number of users" were having problems with Google Mail. "We know how important Gmail is to our users so we take this very seriously," it added. Google directed people to its mail support page for further status updates.

Microsoft did not let the opportunity to poke fun at its rival pass it by. ''Need a new email account? Take a look at windowslive.co.uk - awesome!'' twittered Mel Carson, Microsoft's advertising community blogger.

More than a million business around the world use Google's professional suite of applications, including e-mail. Google itself relies on the service and press spokespeople for the firm were unable to e-mail journalists with statements regarding the problem. The "premier edition" of the Apps service costs $50 per user for a year.

Last August, Gmail had three significant outages that affected not only individual consumers of the free Web mail service but also companies and organisations paying for Apps Premier. To compensate for the downtime, Google decided to extend a credit to all Apps Premier customers and also said it would get better at notifying people of problems.

After the incident Todd Jackson, product manager for Google Mail, said in a blog post: "We're conducting a full review of what went wrong and moving quickly to update our internal systems and procedures accordingly."

Some users reported that Google Mail was working on G1 mobile phones, which are powered by Google's Android operating system. Google Mail also appeared to be working if accessed through a third-party mail-reading program configured to send and receive e-mail using the Imap mail protocol.