[stevekemp]

I wrote a console-based mail client, which was 25% C++ and 75% Lua for defining the UI and the processing.

It never got too popular, but I had users for a few years and I can honestly say MIME was the bane of my life for most of those years.

[thedanbob]

Indeed. A big chunk of my email parser deals with missing or incorrect content headers. Most of the rest attempts to sensibly interpret the infinite combinations of parts found in multipart (and single-part!) emails.