@jef My 'real' (N)MH setup runs everything through a giant sed script[1] to drop a ton of headers, among other things, but I decided not to try to teach MH-E all of that. Or the smaller, more brute force list exmh sometimes uses.
1: I was more inclined to be clever back in the days when I first started writing this sed monstrosity, which was ... a while ago. It should not be in sed. It uses sed tricks. Too many sed tricks.