[captn3m0]

The clients also need to focus on this. Apple Mail on iOS uses plain text variant to show snippets, but if you try to expand the email, it only supports HTML, without a fallback to plain text. This is often the case on slow internet.

[fanf2]

That isn’t true: Apple Mail is perfectly capable of showing plain-text-only messages.

[joaonmatos]

The post you're responding to probably meant in the event of alternative HTML+text emails. Obviously if the email is plain text-only it won't invent HTML to show the user...