Hello, You should be opening port 443 not port 80. That is you should be using SSL rather than a clear connection. Bill > -----Original Message----- > From: Mark Meelhuysen [mailto:m.meelhuysen@xxxxxx] > Sent: Saturday, May 14, 2005 1:25 PM > To: [ExchangeList] > Subject: [exchangelist] Re: RPC over HTTP question > > http://www.MSExchange.org/ > > I also have a question about this option. When I want to use Exchange over > http, do I need to open any extra ports on my firewall? Besides port 80 > ofcourse.