[yid]

That is actually remarkably clever. Spam would indeed seem to be an excellent vector for sending hidden messages!

[wrongc0ntinent]

What in this makes it get past spam filters?

[sp332]

It doesn't matter, as long as it still gets delivered to a spam folder, you can still retrieve the message.

[Zuider]

It doesn't have to get past spam filters. Normally spam is held in the spam bin for 30 days.