Curious to see just how extensively Yahoo is checking for subject lines even more suspicious than "Photos", I ran a little experiment to see what else might set them off. FYI, messages with the following subject lines all went thru just fine:
• This Is Spam
• Pornography Attached
• Biggus Dickus [apologies to Monty Python]
• Nigerian Money Laundering Scam
• PEN IS mightier than sword
• Malicious Virus Enclosed
But at least we're safe from "Photos".