The best combination of efficiency and accuracy for this message would
have been:
multipart/mixed
-> multipart/alternative
-> multipart/mixed
-> text/plain
-> application/pdf (reference, no content)
`-> text/plain
`-> multipart/mixed
|-> text/html
|-> application/pdf (reference, no content)
`-> text/html
`-> application/pdf (referent)
... but mutt doesn't support cid: references, so this wouldn't help
us. :/
If you have ideas for how mutt could deal with this conundrum in a way
that's compliant, consistent, and user-centered, I'm interested to hear.
I'm not sure whether I'll have time to update the code, but it would be
good to get the ideas onto the table.