JMS Messages not reaching the destination

Hi,

I am working on weblogic application server and have distributed servers which communicate with weblogic using JMS . Of recent my messages were being posted from the controller(on weblogic ) to the distributed server but were not picked up by the remote server . However , by changing the smtp server in my environment settings the messages started getting picked up on the remote server . What i cannot understand is the dependency between JMS and SMTP server . Can someone please explain me .

Regards.