How do I disable all HTML in incoming email messages?

Some of the senders are corporations I am doing business with. They will not make an exception for a few people. The reason I want to disable to HTML is because of certain usability problems, such as gray text on a white background, which I find very hard to read. It is not just a personal preference.

I don't mind rich text in email, so long as it does not affect readability.

In my browser, Firefox, I use Stylish to force most pages to display black text on a pale yellow background. Yes, this is how I am viewing this forum site.

Thanks for the help. The solution is to go back to using a more configurable email client (Thunderbird) until Mail.app is fixed. Configurability is often my top criterion in picking a software application.

It's not a matter of rejecting messages that contain HTML. That would be easy using a filter.

The issue is displaying HTML messages as plain text, which Golden Shoes just kindly showed me how to do. I can still read HTML messages, it's just that they appear as plain text.

Actually, apple.com makes such heavy use of very light gray text on a white background, that I've given up using it except on my own machine, which I have set up to change that. Some web sites have an option to change how they're viewed.

I decided to switch to Mail.app, because it uses the better built-in Mac dictionary and uses all of my special keyboard shortcuts.

Oh BTW, where can I find some documentation on all of these hidden settings? I have no problem finding them. I know how to read plists. I want to know what they mean.

Thank you. That solved it. I'll give Mail.app another try.