BPL could send the newsletter in multipart mime format which allows the email client to choose the version it can display best. This is like a bundle with a text and html version wrapped up together, upon display one or the other is used by the client.
Later with fancier user prefs in MY ACCOUNT, individuals could opt for one or the other and only receive that version, saving bandwidth and file size.
There are barely any email clients left that can't negotiate the multipart mime protocol. Even AOL finally figured it out. It must be coded perfectly though or you will get display inconsistencies (end of line characters must be correct). I would suggest a third party newsletter publishing vendor, but I know BPL likes to roll their own gear from scratch.