It would seem that there would be a way to use GNU Mailutils to examine the parts of a multipart email, as with the mmh command mhlist -file amsg.eml and to extract selected parts with the Transfer-Encoding undone as with the (unfortunately buggy) mmh command show -file amsg.eml -part 2
I have installed the package with Guile bindings thinking that might be helpful. Looking through the Mailutils documentation I am failing to find out any way of approaching this problem with or without Guile. I am imagining that I need to map or iterate over all messages in a file (I use mh, so there's only going to be one) and then map or iterate over the parts. Maybe I'm thinking about this the wrong way? I appreciate any assistance. If I can get this to work I will write up what I learn to hopefully assist others.