Google has claimed that its Gmail service has overtaken Microsoft's Hotmail as the world's most popular webmail service, with more than 425 million actives users.
The Gmail figures were revealed by Sundar Pichal, a senior vice president for Chrome and Apps at Google.
While it is likely that plenty of people will have multiple Gmail accounts, the numbers are still staggering – equivalent to nearly a fifth of the total number of global internet users.
The firm also boasted of having five million businesses using its Google Apps service, as well as 66 of the top 100 universities in the US, and government institutions in 45 of the 50 US states, also using its cloud-hosted tools.
The latest figures would represent significant growth for Gmail. In January, Google had said it had 350 million active Gmail users.
Not everyone agrees with Google's claims, however,
According to the most recent figures from internet analysis group ComScore, in May, Microsoft's Hotmail had 325 million unique visitors, with Yahoo claiming 298 million. According to its calculations, however, Google had just 289 million users.
If Google can independently verify that it has stolen Microsoft's webmail crown it would be something of a watershed moment for the IT industry.
Gmail was one of the company's first big plays outside its core search technology, and the launch of the service provided the first inklings that the Google was intent on disrupting Microsoft's business.
Since 2004, Google has also taken on Microsoft through the release of its cloud-based productivity suite and developed a serious challenger to Internet Explorer and Firefox with its Chrome browser.