[otrs] Can't connect to: http://otrs.org/product.xml (500 Can't connect to otrs.org:80 (Connection refused))

Hi.. I have searched on the web but no success. Does anybody have an idea on how to solve this error on the DashBoard of OTRS page? Can't connect to: http://otrs.org/product.xml (500 Can't connect to otrs.org:80 (Connection refused)) and this one: Can't connect to: http://www.otrs.com/en/rss.xml I have OTRs server behind a proxy server.How do I say OTRS to use our proxy server? I also setup HTTP_PROXY variable and it does not work. Thanks much!