The Australian Communications and Media Authority (ACMA) said it had searched a home after a tip-off from Dutch authorities.

"Preliminary analysis of the email messages contained in the spam campaign has identified that over two billion emails were sent," acting authority chair Lyn Maddock said.

"Analysis to date has identified that the messages in the spam campaign primarily promoted Viagra products," she said.

A year spamming

Bruce Matthews, manager of ACMA's anti-spam team, said the regulator was working with Dutch telecommunications authority OPTA, who had brought the case to the attention of Australian authorities.

Matthews said he could not comment further as investigations were still underway and would take some months.

OPTA's Danyel Molenaar said a raid on a small Dutch Internet service provider had revealed that an Australian was responsible for the flood of emails, the Australian Associated Press news agency reported Wednesday.

Molenaar said the man rented 35 servers from the Internet service provider to send spam out for at least a year.

"This operation probably sent out billions and billions of emails," he said.

To confirm Australian link

Although the emails appeared to have been sent from overseas, it was an offence under Australian law for an Australian to be involved, ACMA said.

The Australian authority said it was still analysing the information obtained from its raid, and had yet to determine whether there was an Australian link.

Fines for breaching Australia's Spam Act 2003 range up to $500,000 for corporate offenders.