I alerted the LW proggies about this issue when it 1st surfaced. I'm not sure what the outcome will be I haven't heard back. It may take a while to find a solution ... I don't know.

It's possible that this isn't true spam but just fallout. It can happen that all results bearing addresses used by spammers are filtered out and you receive only the red herrings they emit. What's the largest file you've noticed this problem with? If it's in the Sub-Meg area I wouldn't be worried. If it's several hundred Megabytes this might be interesting.