Google’s Gmail platform could have ousted Hotmail to become the most popular email service in the world, reports.

Gmail now claims to have 425 million monthly active users across the world, which would push it above Hotmail for the first time ever. The figures, however, are contentious.

Yahoo Mail was once reigning champion, but an exodus to Hotmail and Gmail brought an end to its popularity. Afterwards, Hotmail took the accolade and remained the most popular service for many years and was the most popular service for businesses sending out email marketing.

In 2011, on its 15 year anniversary, Hotmail claimed to have 360 million unique users a month. After years on top, however, Hotmail has seen its number one position taken by Google, which is thought to have added around 75 million users in 2012 alone.

Google’s own figures may be slightly skewed, however, as results from researchers ComScore actually put Google in third place, claiming it has 289 million users compared to Hotmail’s 325 million and Yahoo’s 298 million.

Unsurprisingly, Hotmail and Yahoo were keen to agree with the numbers put forward by ComScore, whilst Google spokespeople claim they do not make comment on third-party results.

Comscore VP Andrew Lipsman, meanwhile, told that their data was based on global unique visitors from home and business users, which could leave out mobile browsers or those in internet cafés.

“There are going to be some users that are left out,” he added.