Found this interesting post over at the Bly.com Blog. He lists some reasons why writing benefits into your headlines just doesn’t seem to work anymore.
Reason #2: Your benefit head screams, “THIS IS ANOTHER AD!”
I think you can apply these same ideas to email subject lines.
How many emails come into your inbox every day? For me, it’s about 500 or so (that’s just at the office). For my business partners, they get a few thousand a day (because they manage so many websites). People are constantly bombarded by advertising, so why would they open another email with a subject line that screams, "THIS IS ANOTHER AD! OPEN ME!"
We recently compared subject lines from over 40 million emails sent from MailChimp, to see if we could find any correlation between subject lines and open rates. We found that the best subject lines tell what’s inside, while the worst subject lines sell what’s inside. Click for some examples.