We are running into a strange issue where we get messages queuing on our Ironport device and not delivering when we introduce a load-balancer in front of our CAS array. As soon as we remove the LB, set DNS back in order, flush the DNS cache on the Ironport all the messages start flowing. This only affect mail coming from outside of our network.
Does anyone have any experience with this mail flow: Outside email -> Ironport -> Kemp LB -> CAS Array ?
The specs are: Exchange 2010, Ironport C350, Kemp 7-0.4.
Any help is greatly appreciated.