Is there a US government authority you can contact if you want to stop all junk mail?
No there isn't. Junk mail as you know is just a form of
advertising. You should try going on a good anti spyware such as
free AVG off the web (I use it.) Go on www.google.com Type in: Free
AVG anti spyware The downloading is simple and it will
automatically up-date itself on your computer. The best of all IT'S
FREE! * There is no US governmental agency but a consumer wishing
to be removed from junk mailing lists of any type (US Post, emil
etc. and telemarketer list, etc.) can find the information for
doing so at Consumer Assistance Direct Marketing Association site.