IT support services and managers are spending more than five million working hours a year, worth more than £140 million, sifting through their spam filters for valid emails that may have been junked, according to a new survey.

Email management service provider Mimecast, found that 26 per cent of surveyed IT managers checked their email at least once a day, while 12 per cent checked it twice daily. Allowing for ten minutes per check, the firm estimated that lack of confidence in the accuracy of spam filters was causing businesses to lose 5.85 million working hours.

Peter Bauer, chief executive of Mimecast, told Computer Weekly that the inefficiencies in many anti-spam products were caused by their content-scoring approach to identifying spam.

He told the website: "This approach is flawed because it looks at the actual content of a message and calculates a score based on the type of words and links, but many legitimate emails in the legal, pharmaceutical and financial sectors include content associated with spam."

According to the latest figures from security software firm MessageLabs, one in every 48 sent emails now contains a virus, with most people receiving at least one such email every day.

According to recent survey by Connect, the two biggest IT headaches for businesses were 'everyday hassles with IT' (37 per cent) and 'security concerns' (32 per cent)