We currently have three exchange 2003 servers in a cluster two of them have a smart host to one exchange server that handles all mail outbound and in bound. i.e. server1 server2 smarthosted to server3 which handles all inbound and outbound traffic. The issue is some external mail is being delivered to certain domains such as gmail,msn,hotmail, and others but its not being delivered to aol,comcast.net, other others.
It has been working fine just recently started to happen. I have check to see if we our i.p. has been blacklisted and it has not. i can telnet to these domains that are not receiving our messages. i have check out reverse dns lookup check out fine.
All servers are behind a barracuda 400 spam firewall but it does not check outbound mail.
Thank you in advanced.