IDoc - XI - Web Service configuration

Hallo

This is the problem we are facing :

We get an IDoc as Inbound, do some mapping and then send it to a WebService. The problem is that when we do so, we get a series of errors. Apparently the problem is that when the web service receives our messages it replies with a (simple) message as well. The point is that as far as I know IDocs cannot be configured for synchronous mode, (and when we tried it we failed) so we have nothing to do with the incoming message.

these are the messages from the Integration Monitoring/Message Monitoring

Error Category OUTBINDING

Error Code CO_TXT_ROUTING_BACK_ERROR

We don't have access to the Receiver System and the WSDL file is sent by them