ok over the week end we setup exchange 2003 clusters and moved all the mailboxes over. before the swich over you can see the external IP address that exchange is identifying itself is the correct 195.157.133.93 (this is a header from hotmail): MIME-Version: 1.0 Received: from exwby002.fhbertling.local ([195.157.133.93]) by bay0-mc4-f17.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.2668); Tue, 27 Mar 2007 09:14:47 -0700 here is a header as they appear now in hotmail: MIME-Version: 1.0 Received: from EXCHANGE.fhbertling.local ([195.157.133.90]) by bay0-mc8-f9.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.2668); Mon, 30 Jul 2007 08:27:05 -0700 you can see that now exchange is using 195.157.133.90 to send mails out, this is the IP address of our firewall, which is our gateway out to the WWW. 1 to 1 NAT is setup to point the internal private address of the exchange VS to 195.157.133.93, on incoming it is working fine but on out going it is using the firewall address. this is causing some bounce backs from some domain like aol.com for e.g. who use reverse dns lookups to validate the domain for spam. what can we try to do to force exchange to use 195.157.133.93 when sending? will be extremely happy if some one can solve this mystery! thanks allot myk3

This is going to be pure network related. If you have a networking department or someone responsible for the firewall/router, they need to fix this. Essentially, you need a static route that makes all the traffic go out to the right address. There is not going to be anything in Exchange that will effect this.

thanks, but i have looked in our sonicwall and there isnt any thing i can see that will allow me to make a static route. its just nothing regarding DNS or firwall has changed, the only thing that has changed is the server name really, but thanks any way! mike

Dont use Exchange cluster to receive or send direct to Internet, they should be protected from the bad Internet. I would recomend installing 2 more non-clustered servers facing Internet

thanks! thats great for security. but this will still have the same problem with the IP address.

if you have other server sending mail to internet it will be there's IP that is NAT in Firewall and this will protect you Exchange cluster. Its the same if you have a cluster, its the individual cluster nodes IP's that is NAT in Firewall. and the nodes name, it will not be the virtual IP and name that is used when sending