Microsoft will start charging Outlook users for being able to access their Hotmail accounts.

The charge will start from today on all new Hotmail accounts. Existing Hotmail users will be require to become subscribers in the coming months and the feature will no longer be free from April, a spokesman said.

The software giant claims that the move is not to increase the number of paying Hotmail users, however, but because the feature is being abused by spammers. Brooke Richardson, lead product manager for MSN at Microsoft said: "Essentially what spammers do is create scripts so they can rapid-fire e-mail from Outlook or Outlook Express and pop off a hundred e-mails from each of those Hotmail accounts in rapid succession. On certain days we have seen tens of thousands of Hotmail accounts set up and spamming in this matter."

The Hotmail and MSN mail feature is known as WebDAV, after the Web-based Distributed Authoring and Versioning protocol that enables it. It is enabled on about five percent, or 9.4 million, of the 187 million active Hotmail accounts, according to Richardson.

While the decision to make the link with Outlook or Outlook Express a paid service won't be welcome news to some users, Microsoft had to take the step "for the greater good" of the Hotmail and e-mail community, Richardson said. Rival Web-based e-mail providers such as Yahoo already charge for a similar service.

Microsoft has taken various measures to prevent abuse of Hotmail by spammers including limiting outgoing messages to 100 per day (on free accounts) and an extra validation requirement when signing up for an account. "We do a lot of stuff in terms of understanding the characteristics of spammers so we can watch for them and shut them down when we see them," she said.

Users who want to use WebDAV to link their Hotmail or MSN mail to an Outlook can subscribe to Hotmail Plus, which also offers 2GB of e-mail space and an account that doesn't expire, for $19.95 per year, or to MSN Premium for $99.95 a year.