Ok, ok - I'll answer this one. I wasn't responsible for these names (I'm very supersitious about machine names), but the theme for the junk filter machines was / is something like "tough guy movies" (I think the 1974 "Death Wish" and 1976 "The Enforcer" are the basis for those two machines). I guess one could make some interesting arguments about spam assassination and vigilante justice, but the basic idea is to get tough with your spam.
Maybe not cheerful, but hey - it's less boring than fltr-in01, right? You can always submit a support request and ask that future machines be named "fluffy" and "muffy", or "cumulus" and "nimbus" or something nice and happy and fluffy like that.
I wouldn't worry too much about warnings from dnsreport.com. I think this is an overly strict interpretation of rfc821 / 2821 - all it says is that that section of the machine's SMTP banner should have the machine's fully qualified hostname. In any event, it's not a problem in actual practice... and as they say, stuff that says "warn" is usually minor, and often not worth pursuing. I find the dnsreport tool annoying in that regard, because a lot of times, people get all hot and bothered about things that aren't really a big deal. Useful tool... if you understand how to interpret the results and know when something is or isn't a real problem.