Plain text alternative to web page

[jofabcat]

I want to include a plain text alternative to a web page. I have followed the advice in the user guide:
'add an alternative plain text version as with Text/HTML format, add two line-breaks and the text right below'
however the text is still not appearing?
can anyone help?

 

[stanbusk]

The text will appear to recipient which mail reader software is unable to render HTML.