The volume of spam e-mails fell this month to the lowest level in nearly two years, according to a report from Symantec’s MessageLabs. Spam accounts for 78.6 percent of e-mail traffic, down 3.1 percent from December and 5.3 percent from January 2010. The previous low-water mark was in March 2009 when 75.7 percent of e-mail traffic was spam…