Last December, after signing on with a spam-filtering service, national law firm Gray Cary had about 47% of its 661,000 incoming messages blocked. Last month, the firm saw about 65% of its 1.1 million messages banned from arriving in end users' mailboxes.

With spam volumes showing no signs of falling, Gray Cary has had no choice but to have a solid anti-spam system in place, says CTO Don Jaycox.

"We pretty much used to hear constant complaints, but now I just don't hear them," he says.

Gray Cary's anti-spam needs are being met by FrontBridge Technologies, a provider of messaging security services that last week announced it has raised $8 million in venture funding.

While rampant spam, in addition to proliferating viruses, have made e-mail management a huge challenge for many companies, the onslaught has been a bonanza for vendors. Kirk Walden, national director of venture capital research at PricewaterhouseCoopers, says nearly $125 million has been invested in e-mail management companies over the past year and a half, with many targeting the spam problem.

FrontBridge received its latest investment from BA Venture Partners and Sierra Ventures, and now has compiled $18 million in funding over three rounds. The company started up in 1999 and began offering services two years ago. FrontBridge says it has roughly 700 paying customers (the service costs about $18 per user) with anywhere from 100 to 100,000 seats.

The company plans to use the funds to expand its sales team and network of data centers. The data centers - FrontBridge has seven in the U.S. - intercept e-mail on its way into customer networks and ensure it's legitimate (and virus-free, if the customer chooses to use the vendor's anti-virus service) before forwarding it. New data centers are slotted for London and Singapore.

FrontBridge uses a variety of techniques to filter out spam. These include a proprietary blacklist, rules-based scoring and a "fingerprinting" technique that lets the company identify spam based on mail filtered among its entire customer base. Customers can use console software to examine their spam situation and review reports.

The company says only one in 250,000 legitimate messages is filtered out mistakenly as spam. That's a good thing, Jaycox says, because the law firm can't afford to have its dealings with clients compromised.