If it's important that the MDB *not* run within the context of a tx, you can use bean managed transactions and just not start one. Or, use TX_NOT_SUPPORTED.
About tx inflow, while there's no prohibition against consuming a JMS message in an MDB from a connector that flows in transactions, that's certainly not the intended use case. Tx inflow was mainly added to support the non - JMS MDB case.
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