A Melbourne accounting firm has saved $600 in excess bandwidth costs by using a hosted reputation spam filter.

Medium-size accountancy and business advisory firm Lowe Lippmann was established in 1947 and has individual, SMB, enterprise, and government clients.

Lowe Lippmann information systems manager Ray Finck said its network was overloaded by some 6500 spam emails a day, which was crashing live connections to clients and blowing out bandwidth costs.

"[Excess bandwidth] was typically costing us $600 per month in additional costs," Finck said.

"Apart from the nuisance of unsolicited e-mail for the user, the overriding problem was that it also caused network congestion meaning that live connections to the Australian Taxation Office sometimes failed.

"Spam can also carry viruses and phishing attacks [which] further added to the threat and the urgency for it to be stopped."

Finck said spam accounted for almost 10Gb of the companies 30Gb bandwidth limit a month, noting only 11 percent of the 7000 e-mails the company received last December were legitimate.

The company overlaid its five year old Websense e-mail filter with an on-demand anti-spam solution from the same vendor, after evaluating basic IP-based filtering.

Bandwidth consumption has since dropped from a peak of 35.6Gb in August to an average of 25Gb a month.

"On one day 7000 e-mails hit the filtering service of which 500 to 600 were legitimate," Finck said.

He said 136,800 spam e-mails were trapped last November which decreased bandwidth usage by 15 percent..