MQ has no concept of a duplicate message.

You can put two "identical" messages on the queue if you like, but that's application-level logic. Once you have got a good return code from the send() operation, the message is (subject to transactionality and persistence options) there forever until someone removes it.

Even if you did something expensive like scan the existing messages on a queue before putting a new one, that would not help you if someone has already removed the "identical" message.