Damn you, autocorrect!
Anyway, the way I see it, Google may have set up a script for it. I wouldn't want to be the one to test it though.
Google scans email. We know this.
It's possible for a computer to recognize fleshtones and even distinguish nudity.
It's plausible a computer could make a reasonable guess as to the age of the subject in an image, especially if there are context clues in the text around the image.
A computer could thus identify a naked kid.
If a naked kid were identified, the computer could then check who the image came from -- does the user communicate with them regularly? Did the user send it to himself?
If yes, fire off alert. Possible human review before final submission to authorities.
If no, hopefully discard the result. After all, wouldn't want Nanaki
's hypothetical spam-leads-to-prison situation to come true.
Solution: Child Pornography traders become spammers.
Oh crap.