So I'm wondering a bit here - I've seen an implementation where emails to send only have html versions, but as part of the sending process the html is run through a Lynx browser process with the -dump command to get the plain text, which is included as the text/plain part of the email.

Is there actual value to this? e.g. Is the output of Lynx's text dump better for plain-text email clients than whatever they'd display for html emails?

I've personally converted html to plaintext with beautifulsoup in python, and used that as the plaintext version. Did not have complaints, but I honestly don't know who actually reads the non-html version.

Some (old?) spam filters may be triggered by html only emails.