PROBLEM: We are publishing an Exchange Server 2007 SP2 NLB for CAS and HT (inbound smtp) roles through ISA Server 2006 array. When one of the CAS/HT servers becomes unresponsive the ISA Server rule does not notice this and continues to send all traffic to the same Exchange Server. We need the ISA Server array to load balance the incoming SMTP traffic to both servers and not have it send all traffic to one.We have two Exchange servers running Windows Server 2008 with Exchange Server 2007 SP2. The servers are virtual machines running on a six node Microsoft Hyper-V cluster. The Exchange NLB settings for port affinity are set to single and the ISA Server publishing rule is set to "Requests appear to come from the ISA Server computer." Why is the Exchange Server NLB not load balancing incoming connections and failing over to the other NLB node when necessary? Does the affinity need to be changed to none to allow the traffic sent through the ISA Server array to be load-balanced properly?Any help would be greatly appreciated.

Is NLB running on the ISA end or the Exchange end?Active Directory, 4th Edition - www.briandesmond.com/ad4/

When there is a Failover, the Exchange server failing is UP, shutdown? restarting? Exchange services Down?CapecolMCSA - MCTS Exchange Server 2007 - 2010Blog: http://capecol.spaces.live.com/default.aspx

Please verify the NLB configuration (Reference) Is there any related event in the application log on the exchange servers? Please run ExBPA against the exchange servers for health check Do you use Unicast with single NIC? Hosts can’t talk to each other in this mode, to enable hosts to talk to each other, please view KB 898867 Does HC01 can ping HC02’s IP from command window? Try to telnet default <server> receive connector by using the FQDN of the servers themselves Notes: In this case hc01.domain.com (The one gets all requests) and hc02.domain.com Testing Server’s NLB Resiliency, let’s drainstop the HC01, see if client has any issue to communicate with HC02 (In un-produced time) Open NLB Manager->right-click HC01->select “Drainstop”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

hi , why not make the load balancing on the exchange servers & add the specifc ports & also add port 25 in the NLB& make the affinity to none