I'm receiving below message: 451 4.4.0 primary target IP address responded with "421.4.4.2 unable to connect."attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts I have WNLB CAS/HUB. I can telnet to vIP (NLB) but individual CAS/HUB servers telnet errors ("Could not open connection to the host, on port 25: Connect failed. Please help. Thanks

Whether it’s an inbound mail flow issue, outbound mail flow issue, or both? The firewall, or anti-virus software can cause the similar symptom, please disable all third party software, and the firewall on the exchange servers, and then see if the issue still appears Incoming mail flow stops, or the SMTP service fails when you try to fail over a node in Exchange Server 2003 or in Exchange 2000 Server after you install McAfee VirusScan Enterprise Please use the tool “PortQry” to the status of the port 25 (KB 832919) portqry -n myserver -e 25 Please enable the protocol logging on the connectors, and check the log files (Reference)James Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com

James, thank you for responding to my post. Corrections on my first post: I'm able to telnet all CAS/HUB Servers on both NLB IPs, NLB vIP and Non-NLB IPs. Issue is for Outbound ONLY. Does this mean that my port forwarding from CAS/HUB server using NLB vIP to Public IP at firewall is incorrect meaning should my FW have SMTP-Out config as individual IPs for the CAS/HUB server to Public IP at firewall? I'm running Exchange 2010 on Windows Server 2008 R2 (Host/Guest). Update: corrections/additions

“Network Load Balancing runs as a network driver logically beneath higher-level application protocols, such as HTTP and FTP. On each cluster host, the driver acts as a filter between the network adapter’s driver and the TCP/IP stack, allowing a portion of the incoming network traffic to be received by the host. This is how incoming client requests are partitioned and load-balanced among the cluster hosts” ---------Refer to <How Network Load Balancing Technology Works> I don’t think that NLB can be used for outbound traffic. Yet, as I’m not an expert of NLB, please use the “Windows Servers” forum for the question about NLBJames Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com

James, My firewall team last night changed outgoing IP to internal IP of each CAS/HUB server. Outgoing e-mails are processing now. Thanks for help. Kris