http://blog.csdn.net/hiping_cao/article/details/8976153
http://blog.csdn.net/kai_wei_zhang/article/details/7982371
http://blog.csdn.net/t12x3456/article/details/7636416
http://blog.csdn.net/yxfei666/article/details/7328099
http://stackoverflow.com/questions/4960556/javamail-attachment-from-string-encoding-problem