If one side of your application is JMS and the other is MQ application (i.e, MQ Java or MQ C++); in order for the MQ application to read the message JMS sent you need to configure the "TARGCLIENT" field in you JMS Queue or Topic to be "MQ".
For example
InitCtx> define q(TESTQ) TARGCLIENT(MQ)
JMS uses RFH2 headers, where MQ uses RFH1 headers. So if you sent the message from JMS application without specifying TARGCLIENT to be MQ the messgae will have RFH2 headers and MQ applications wouldn't know what to do with it.
Good luck