MessageLabs reported that the percentage of "unauthorised" e-mails sent had increased from under 40% in April to 55.1% of all e-mails sent during May. SpamTrap, another filtering company, revealed that in the same month 55.8% of all e-mails sent to its customers were spam.
The figures come just a few days after Ryan Hamlin, general manager of Microsoft's anti-spam technology and strategy group, told a conference at the company's Mountain View, California campus that the volume of spam sent is expected to increase to 65% of all e-mail in 2004.
He added that concerted efforts by the software industry and government should eventually stop spam, although it may take up to two years.