Are you being sarcastic? Very hard probably.

I’m ... not sure. There’s a limit to how complicated emails are in 99% of non-spam HTML emails, right? You’re working with a limited subset of HTML meant to be reflowed to small screens pretty easily, and the task here is to extract text content into a form that can then be shown in a terminal.

I would — at the very least — think it was worth giving a go

You might as well just use any other email client then and it'll be more efficient.