There is a bug in IBM XMS for .NET that causes grouped messages to be written incorrectly. Grouping needs to take place in both the XMS layer and the MQ layer. In the XMS layer, properties JMSXGroupID, JMSXGroupSeq, and JMS_IBM_Last_Msg_In_Group are stored in the RFH2 header. When XMS hands the message off to the MQ layer, it is supposed to use the RHF2 header properties to set fields in the MQ message descriptor. Specifically, when JMS_IBM_Last_Msg_In_Group is true, the message descriptor MsgFlags...