what is the content-type 'application/EDIINT'?


We have strange phenomenon on our server.
We sends a EDIINT message via AS2 requesting a synchronous MDN to our trading partner using WM.
This process work well.
Message is ok but MDN did not send back.
We received below.

HTTP/1.1 200 OK
Set-Cookie: ssnid=; path=/; HttpOnly
Content-Type: application/EDIINT; charset=UTF-8
Connection: close
Content-Length: 0

My partner has confirmed that the MDN content-type was set to multipart/report but the MDN content-type that I received was set to application/EDIINT.
I can find this type ‘application/EDIINT’ only WM users forum.

Then, what is ‘application/EDIINT’?
In what case does it occur?
Could anyone please help on this issue?