In another reminder of technology’s quantum leaps, Yahoo!’s free e-mail service will provide unlimited storage space to its nearly 250 million users worldwide – a concept that seemed unfathomable just a few years ago.

With the move, Yahoo!! will trump its two largest rivals in free e-mail, Microsoft and Google which currently provide 2Gb and 2.8Gb of free storage respectively. Yahoo!’s e-mail users currently get 1Gb of storage.

Yahoo! plans to start lifting space constraints in May, but it will be several months before all of Yahoo!’s e-mail users have infinite storage space.

AOL, the fourth largest e-mail provider, began offering free unlimited storage last summer, but Yahoo!’s commitment will require substantially more resources because its e-mail service is nearly five times larger than AOL’s.

“We’re psyched to be breaking new ground in the digital storage frontier by giving our users the freedom to never worry about deleting old messages again,” John Kremer, a Yahoo! vice president of mail, wrote in an announcement posted on the company’s website.

It is only three years since the company offered only 4Mb of free storage and charged nearly $50 (£27) for 100Mb of extra space. The main impetus to change was the arrival in April 2004 of Google’s Gmail, which initially offered 1Gb of space when it launched. Last month, Google dropped the invitation-only restriction on its mail service and opened the service to all.

The expansion has been driven partly by the fall in the cost of storage and partly because companies have been willing to spend large amounts of money on adding extra memory. They consider e-mail to be a powerful magnet that spurs frequent visits, and thus more opportunities to sell adverts. Meanwhile, the proliferation of digital media – from photos to music – has increased the demand for more storage.

When Yahoo! began offering free e-mail ten years ago, the capacity of the entire service topped out at 200Gb. Now 200Gb of mail arrives at Yahoo! every ten minutes, Mr Kremer wrote.

Yahoo!’s expansion will be largely irrelevant to many e-mail users who haven’t come close to approaching their current limit. Microsoft said it had no plans to increase storage space in Hotmail, and Google said it intended to keep to its current policy of adding about 145Mb of space per year.