In this moment we have a issue with the mic cause we are using the AS2SignatureAlgorithm.SHA256WITHRSA and its possible that when you try to send the algorithm directly from the message you start to get issues. if you know that MD5 works why is required to change it?

By the way like i told you we are testing with SHA256WITHRSA and apparently doesnt works. i just make some changes to use SHA2WITHRSA cause in some article i read that the support algorithm for signature are SHA-1 and MD5, did you test any other the error that we are receiving is the next one.

org.apache.http.HttpException: Failed to encode MIC
at org.apache.camel.component.as2.api.util.MicUtils.createReceivedContentMic(MicUtils.java:111)
at org.apache.camel.component.as2.api.entity.AS2MessageDispositionNotificationEntity.<init>(AS2MessageDispositionNotificationEntity.java:95)
at org.apache.camel.component.as2.api.entity.DispositionNotificationMultipartReportEntity.<init>(DispositionNotificationMultipartReportEntity.java:66)
at org.apache.camel.component.as2.api.protocol.ResponseMDN.process(ResponseMDN.java:157)
at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:142)
at org.apache.http.protocol.HttpService.handleRequest(HttpService.java:360)
at org.apache.camel.component.as2.api.AS2ServerConnection$RequestHandlerThread.run(AS2ServerConnection.java:163)
Caused by: java.lang.IllegalArgumentException: Data must be specified
at org.apache.camel.util.ObjectHelper.notNull(ObjectHelper.java:153)
at org.apache.camel.component.as2.api.util.EntityUtils.encode(EntityUtils.java:89)
at org.apache.camel.component.as2.api.util.MicUtils$ReceivedContentMic.<init>(MicUtils.java:48)
at org.apache.camel.component.as2.api.util.MicUtils.createReceivedContentMic(MicUtils.java:109)
... 6 common frames omitted

Let me know if you test with other algorithms before to try to do the thing that you want to do.