Yankees15 posted earlier with the headline "Kenny goes Postal"
Postal= "Nuts" I have got a game also called Postal but there is no "Post" or mailman in it
Can anyone provide an explanation how this word was linked with being nutty?

Here's the complete history-
http://crime.about.com/od/issues/a/aa040717.htm

The term "going postal" came into our vocabulary on August 20, 1986, at a post office in Edmond, Oklahoma, when employee Patrick Henry Sherrill, known as "Crazy Pat" to some who knew him, shot two of his supervisors then continued his rampage killing a total of 14 co-workers and injuring seven others. Ultimately he turned the gun on himself and committed suicide. After this incident, there seemed to be a rash of work-related violence in post offices, hence the term, "going postal." What motivated Sherrill's action? He believed he was about to lose his job, investigators found. Experts believe the availability of firearms (75 percent of these incidents involve guns) combined with work-related stress, smaller workforce, decreasing wages and the loss of job security are the main contributors to the violence.

Thanks for that,There is nothing at Answers.com except a reference to the computer game(same name) which was banned in some countries because of excessive violence

You're welcome! It's a term used frequently at my former place of employment. But it's not limited to the workplace any more. Anyone under extreme stress is liable to go postal. I never heard of the game but just the title implies a lot of rage and violence.