Spam email is apparently using enough energy a year to power 2.4 million homes, and has a carbon footprint equal to that of 3.1 million cars.

According to an ICF survey commissioned by security company McAfee, the mass of spam sent out amounts to 33 billion kilowatt hours every year, with the UK the joint fourth biggest contributor to spam's carbon footprint

Cole filtered?

The message from McAfee, not surprisingly, is that spam filtering is helping the environment, as well as our inbox sanity.

"As the world faces the growing problem of climate change, this study highlights that spam has an immense financial, personal and environmental impact on businesses and individuals," said Jeff Green, senior vice president of product development at McAfee.

"Stopping spam at its source, as well as investing in state-of-the-art spam filtering technology, will save time and money and will pay dividends to the planet by reducing carbon emissions as well."