Nearly all of the internet-connected computers that send email are controlled by spammers, according to Return Path, a company that compiles email reputation data.
Of the 20 million IP addresses that send email and are tracked by Return Path, only 0.9 per cent have earned a reputation score that will allow their emails to be delivered to Return Path clients. About 2.5 per cent encounter problems such as spam traps or having garnered too many complaints. But 96.7 per cent score so badly the sending computer is likely to be a hacked PC, the company said.
Spam makes up almost 75 per cent of all messages sent today, according to email security service Postini.