I have two cas servers in my company and one of the cas servers is working fine but the other one is keeping the mails and not submitting them for delivery or even sending out mails. All servers are started and the server is configured for NLB. Need help sorting this out if there is anyone that has any advise, please give cause i have google and tired everything possible known to no success.

Mailflow is done by the HUB servers not the CAS, apart from the submission service on the mbs servers. Check the services on all your servers and see if they are all started. Narrow where the message flow is failing, on the client, mbx or hub server. Check all queues and MT.Sukh

All servers are started and the server is configured for NLB. One or two NIC Adapters and is the NLB configured in unicast or multicast mode?Martina Miskovic

Hi, What is the error? Please verify if the message stays in the outbox folder. If not, please use Queue viewer to check where the message stays. Please run ExBPA to have a health scan of the Exchanage Server.Xiu Zhang TechNet Community Support

Any update?Xiu Zhang TechNet Community Support