According to a recent study by McAfee Inc.,
"spam e-mail is not only a nuisance, but is damaging to the environment
and substantially contributes to green house gas (GHG) emissions."
About 33 billion kilowatt-hours (kWh) or energy is used yearly around
the globe to send, handle and filter out spam emails. This wastage of electricity can power "2.4
million homes" and the GHG emissions are equal to "3.1 million
passenger cars using 2 billion gallons of gasoline." Just imagine the
positive impact caused by taking McColo

offline last year. About 62 trillion spam messages are transmitted
every year and McColo going down provided the same benefit obtained by
removing 2.2 million cars off the road for one day.

"Some important findings from the study include:

• The average GHG emission associated with a single spam message is 0.3
  grams of CO2. That's like driving three feet (one meter); but when
  multiplied by the yearly volume of spam, it is equivalent to driving
  around the earth 1.6 million times.

• 
  Much of the energy consumption associated with spam (nearly 80 percent)
  comes from end-users deleting spam and searching for legitimate e-mail
  (false positives). Spam filtering accounts for just 16 percent of
  spam-related energy use.
• 
  Spam filtering saves 135 TWh of electricity per year. That is
  equivalent to taking 13 million cars off the road.
• 
  If every inbox were protected by a state-of-the-art spam filter,
  organizations and individuals could reduce today’s spam energy by 75
  percent or 25 TWh per year, the equivalent of taking 2.3 million
  cars off the road.
• 
  Countries with greater Internet connectivity and users, such as the
  United States and India, tended to have proportionately higher
  emissions per e-mail users. The United States for example, had
  emissions that were 38 times that of Spain.
• 
  While Canada, China, Brazil, India, the United States and the United
  Kingdom had similar energy use for spam by country, Australia, Germany,
  France, Mexico and Spain tended to come in about 10 percent lower.
  Spain came in at the lowest, with both the smallest amount of e-mail
  that was received as spam and the smallest amount of energy use for
  spam per e-mail user."