[bstsb]

the actual base64 email itself is an HTML document, with a bunch of filler text about metal magnets!

> Hi there, A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction [...]

they sign off the email with a zero-width space set to "font-size: 0" for some reason

[gus_massa]

The text is from https://en.wikipedia.org/wiki/Magnetic_domain that uses a CC BY-SA 4.0. I hope they remembered to add the atribution as requested :)

[tom1337]

Also, the magnet text is not visible:

style="position: absolute; left: -9999px; top:-9999px;display: none"

maybe they try to warm up those emails to use them for other "campaigns" later on...

[mike-cardwell]

The text is added to get around bayesian filters. The spammer doesn't want the text to be displayed to the end user though typically.

[autoexec]

A smart bayesian filter would catch email with invisible text. Legitimate email shouldn't have any, but I have seen it more than once in spam