I have analized my problem: I have configured a newsfeed between two Exchange 5.5 servers and I haven?t problem. Then I have configurated a newsfeed from an Exchange 2000 server and one of the Exchange 5.5 server ; the result is that the message created in the Exchange 5.5 it?s replicated to the Exchange 2000 but not the contrary. The problem is the command IHAVE, the Exchange 5.5 accept this command only if the IP number of Exchange 2000 Server is declared in its configuration, but this server have a dynamic ip in the internet!!! There isn?t problem between two Exchange 5.5 because they use POST for replicate message. Do you know a solution?