Ask HN: What's up with this spam email? Could it be Efail?

I got a strange message yesterday. It makes me wonder about Efail. I don't decode HTML, and fetch no external content, by the way.

In Thunderbird text mode, "----DMMAwGuf 1hTVhVG5 OI0QBVgA ... cROBNJ3k q9IZYLZM rP0GExKW RS----" appears as the message header. Where an image might normally be.

The body requests a quote for storage tanks, and refers to an attached image. But there are no attachments.

Interesting HTML snippets are:

    <div style=3D"display:none;"><span style=3D"font-size:0px;line-height:0px;color:white;background-color:white;">----DMMAwGuf 1hTVhVG5 OI0QBVgA ... cROBNJ3k q9IZYLZM rP0GExKW RS----=0A=0A<br><br></span>

    <div style=3D"display:none;"><span style=3D"font-size:0px;line-height:0px;color:white;background-color:white;">----iAmobekE x8fPP99r k7BqbiXj ... 3zlX0bTK oPoV8ioK 6J5dAT----</span>

It might just be screwed-up text-encoded images. But then why would they do "display:none;" and "font-size:0px;line-height:0px;color:white;background-color:white;" to attempt hiding the text?