If you not have read the book, Enteprise Integration Pattern, read it.
Here come some of the flows and pattern I have used.
First when we have control over the system we can use a lose lose pattern.
The application who produse data have its own message broker to publish message to The integration layer take the message from it. If the integration layer is a own domain the message is transportet to that messabroker in its original format.
After the message is in message broker in the integration domain we can do business logik for the message and write some transformation. We also always validate the message the first thing we do.
If we not have controll over the application the