General
Observe the notes in chapter Ausgehende Kommunikation (von Connect).
Make sure that an HTTP or HTTPS server is configured and that the ICM process is running. The message server provides a list of available serve processes at the following URI:
http://[Message_Server_Host]:[Message_Server_HTTP_Port]/msgserver/text/logon?version=1.2
Alternatively, you can use the Goto -> Services function in transaction SMICM.
HTTP error 404 (Not found)
Make sure that the corresponding service is activated in transaction SICF.