This feature was missing, but a lot of people wanted to have it. Now, in SP2, it is available and very easy to configure.
For that reason, I created a small blog to highlight the configuration and the result.
In a previous SP, the highlighted feature below was not available
Within the receiver AS2 communication channel, make sure to indicate synchronous MDN messages and a reference to a sender AS2 communication channel, getting the incoming MDN message
Create a sender AS2 communication channel that corresponds to the one used in the receiver AS2 communication channel, configured in the previous step.
Use http://testas2.mendelson-e-c.com:8080/webas2/ to look into message content on the Mendelson side.
For the SAP PO monitoring, this is the result(*)
(*) Please note that acknowledgements results are depending on the AS2 receiver capabilities. This example was built using Mendelson AS2