From McAfee and Symantec to Apple and Microsoft, most vendors that make antispam products are failing to fully satisfy customers, according to  survey released Tuesday by the Brockmann & Company.

The best-performing technology by a large margin is made by challenge-response vendors like Sendio and SpamArrest, which challenge the identity of first-time senders, the report states.

But customers rarely are fully satisfied by antispam filters packaged with e-mail clients, hosted e-mail or commercial antivirus software. Too often, the products let spam messages through and mistakenly delete e-mail that’s not spam.

Thirty six percent of companies surveyed have lost business because of legitimate e-mails getting caught in spam filters, says report author Peter Brockmann, president and research director.

“Whatever products they have developed obviously haven’t been working,” Brockmann says.

That’s bad news, as PDF spam seems poised to overtake image spam as the next big problem. “Now it looks like there’s going to be PDF spam, which is even worse for businesspeople,” Brockmann says. “We sign purchase orders and pass contracts back and forth all the time.”

Rather than rate each vendor individually, Brockmann’s survey divides technologies into eight categories. The firm surveyed 520 business employees who work in IT, sales, marketing, finance, human resouces and administration, or are C-level executives.