Can you please rename impl_from_DMUS_PMSG? message_from_DMUS_PMSG or msg_from_DMUS_PMSG; or something else, I don't really mind.
"impl" comes from the "Impl" in IFooImpl COM object names / types so would imply we get from a DMUS_PMSG to a COM object.
The rest looks good, though I'm concerned about the test failure: ```dmime.c:1962: Test failed: got 265``` The MR update should rerun the test and we'll see if it was some transient or the test if "flaky" in the pipeline.\ I've rerun the tests 60+ times but could never get it to fail. As that is a timing test I wonder if the CI box was overloaded at that time.