Delivery specialist FedEx has been accused of "systematically" overcharging its business and government clients for nearly a decade, and an internal company message may be the smoking gun to prove it. The email from a FedEx sales executive was unsealed this week as part of a lawsuit against the company claiming that they overcharged for millions of packages over "many years." According to Bloomberg, the email seems to make the whole case pretty cut and dried. "I have brought this to attention of many people over the past five or six years, including more than one managing director, and no action has been taken to address it,” Alan Elam wrote in an e-mail on Aug. 2, 2011. “My belief is that we are choosing not to fix this issue because it is worth so much…