PI 7.31 Mail Adapter error 554

Hi @ all,

we implemented a scenario between Outlook Exchange Server,  Pi and SAP Backend (receiver).
The scenario work as intended with one exception. Comprised the Mail a picture (jpeg ; gif; png) on the Exchange Server, i get the Response:

com.sap.engine.interfaces.messaging.api.exception.MessagingException: com.sap.aii.af.sdk.xi.srt.BubbleException: Failed to call the endpoint [null "null"]; nested exception caused by: java.io.IOException: server not responding OK to .; 554 Nachricht im SAP System nicht bearbeitbar

                                                                                                                                 (554 Message in SAP system not workable)

Any idea how to fix it??

Kind regards
Sercan