Comment by zuminator

What's more a "professional" CP distributor would at the least encrypt or compress their photos, and probably not even use Gmail, maybe use a hijacked cracked account.* So that would lower the "true" positive rate even further.

*In fact that seems like it could be an effective form of extortion or swatting. Someone with access to your credentials could (threaten to) send CP over your account and ruin your life. Or destroy a small business.