http://mirror.ncsa.uiuc.edu/procmail-faq/
http://www.jaist.ac.jp/~fjt/procmail.html
http://www.hotwired.co.jp/webmonkey/2003/10/index2a.html
http://kinsan.main.jp/wiki/wiki.cgi?page=%A5%E1%A1%BC%A5%EB%CA%DD%C2%B8%B8%CB%A4%CE%B9%BD%C3%DB
http://www.cool-web.com/procsm1.html
http://www.rcnp.osaka-u.ac.jp/Divisions/CN/computer/ibm/manual/procmail/setting_procmail