Python dependencies:
- mail-parser (https://pypi.org/project/mail-parser/, tested with v3.9.3)
- Markdown (https://Python-Markdown.github.io/, tested with v3.1.1)
- python-magic (http://github.com/ahupp/python-magic, tested with v0.4.15)
- libmagic (e.g. libmagic1 on Ubuntu or libmagic in homebrew)
Tested with Python 3.7.3.