Outbound Rest Message failing with error message "Unknown host" and Response body we can see "[ERROR CODE: -1 ]".
Release or Environment
If I try to resolve the host from the node where the instance is running, it returns the same error "Unknown host".By the look of it, that endpoint seems to be running on an internal resource. This most likely means that the endpoint cannot be resolved by the external.
We need to use MID server to access the endpoint or endpoint to need to host to access from the public network
Please check below screenshot to add the MID server on the Rest Message :