The British man taken to court by Microsoft has been prevented from selling lists of email addresses that have then been used by spammers.
Paul Martin McDonald sold email lists that were subsequently used by spammers through his company Bizads.
However, Microsoft successfully argued that, as the owner of web mail service Hotmail, it had experienced loss and damage to its reputation as a result of McDonald's actions.
The software giant was granted a summary judgement after Judge Lewison agreed that Bizads had violated the Privacy and Electronic Communications Regulations (PECR), which includes measures designed to prevent the sending of unsolicited email and is policed by the Information Commissioner’s Office.
Judge Lewison said: 'The evidence plainly established that the business of Bizads was supplying email lists of persons who had not consented to receive direct marketing mail and that it had encouraged purchasers of the lists to send emails to those people.
Although McDonald had not sent spam himself, Judge Lewison said: “The lists contravened regulation 22, as they concerned the sending of unsolicited emails and the words of the Bizads website instigated the sending of emails.”
He agreed that Microsoft had suffered a loss as a result of McDonald's breach of the PECR, awarding the software firm an injunction preventing him from selling lists of emails that may result in commercial emails to Hotmail accounts.
The British Computer Society said the decision has been hailed as a major breakthrough in the fight against spam as it is one of the first times the PECR has been used to stop the sale of email lists for spam.