"It is unlawful for any person to initiate the transmission to a protected computer of a commercial electronic mail message if such person has actual knowledge, or knowledge fairly implied on the basis of objective circumstances, that a subject heading of the message would be likely to mislead a recipient...regarding the contents or subject matter of the message..."
How's that for some legalese? That's the actual language from the CAN-SPAM Act of 2003 (PDF), the law that establishes the rules for commercial email in the United States.
I'm not an attorney, but the intent of that language seems quite clear to me. Put in non-Franken-speak, it can be boiled down to this: Don't send an email with a deceptive subject line.
However, like many laws, it's all about interpretation.
So where does the line get drawn between a creative, compelling email subject line and one that is deceptive (and possibly illegal)?
An interesting conversation has been going on among email marketing folks lately around this very topic. I've argued that there is power in a compelling subject line: If you want people to open your emails, your subject line has to stand out in their (likely crowded) inbox.
That's not to say a "boring" subject line can't also be effective. My colleague Chris Penn proves that point with his weekly newsletter, the subject line of which reads, "Almost Timely News from @cspenn for [date]." The only part of his subject lines that changes week to week is the date, and his open rates have been hovering around 13%.
But a creative, compelling subject line certainly can get your attention. Urban Outfitters is one of my favorite examples. YOLO OMG WTF Sale! was the subject line of a recent email it sent to its list. (Read about more "crazy" subject lines.).