The first live run of the Indian Ocean Tsunami warning system earlier this month turned out to be a bit of a disaster.

Not a natural disaster, but it provided an unexpected result for some users of Apache's SpamAssassin.

Subscribers to the automated e-mail warning system, which sent out an alert for an earthquake off Northern Sumatra that rated 6.7 on the Richter scale, found the Tsunami warning notification deferred as spam.

The problem arises if the open source filter is installed straight out of the box; the messages (usually written in upper case) are not considered spam.

But for anyone who locks down the spam filter, SpamAssassin categorizes the e-mail as spam due to a combination of upper case text in a clear-cut format forwarded by a hidden sender.

With the spam filters locked down, the warning message - written in the original in upper case letters, of: "THERE IS A VERY SMALL POSSIBILITY OF A DESTRUCTIVE LOCAL TSUNAMI IN THE INDIAN OCEAN", rates a spam score of 3.7 out of 10.

Australian National University (ANU) visiting Computer Science Fellow, Tom Worthington, said anything that rates over five is considered to be spam and a 10 is absolutely spam.

"There is also a general concern that the more words the message uses will make the rating go even higher," he said.

"The indicators on the message are typical of what spam software uses - if you work in a government agency there is less of a concern, because the system is set up to receive the warnings but there is always the risk that computer support will install a spam filter for mail and these messages won't get through."

Put simply, these dire warnings of a natural disaster will be blocked because they will be regarded as spam.

"With these sorts of messages you want to make sure they get through ... the other interesting thing is previous tests had this exact problem with the spam filters," Worthington said.

"The Tsunami messages are very official and use clear-cut wording which is setting off the spam filters - they need to change format because part of the problem is that spammers also try to make messages look official."

Worthington said he has since been in contact with the Japan Meteorological Agency which issues bulletins for the Indian Ocean, and with the United Nations Educational, Scientific and Cultural Organization requesting them to redesign the mailouts.