A fault with a .com.au name server prevented users from accessing Web sites and sending mail to other parts of the Internet for about three hours last Thursday.
The problem took place when one of the authorative nameservers for domains ending in .com.au had a problem with the 'zone file', which lists the routes and IP addresses for domain names.
Australian Network Information Centre (Aunic) says the problem began when a server at Melbourne IT, the company which registers domain names, generated an incomplete .com.au zone file.
This was transferred, via an auDA server, to other com.au domain name system's (DNS) secondaries including ns.ripe.net, an authorative nameserver for .com.au operated by Holland-based organisation RIPE.
Most mail servers verify that the sender's mail servers exist before accepting it. If receiving mail servers were directed to the RIPE server to verify a .com.au name, they would have been told the sender's domain did not exist and could have rejected the mail.
Web site visibility was also a victim of the glitch.
According to Aunic, which lists utilities for Internet domain names management within the .au code, this would have affected around 20 per cent of DNS queries for .com.au sub-domains during the outage.
Chris Disspain, the chief executive of the auDA, said it is not known how the glitch was generated.
"Our technical people are talking to [RIPE's] technical people to find out how it occurred," Disspain said.