A fine article on the Smart Insights blog called Which works best? Specific or general subject lines? explains why the number of people opening your emails may not be a good measure of their success. We all know that the subject line is critical in getting people to open the email, so if you’re sending an email where only a proportion of the audience will be interested in the offer, it’s tempting to hide the specificity of the content (as described by the subject line) to maximise the open rate. For example, if your audience comprises red widget buyers and blue widget buyers, and you have a blue widget offer, it’s tempting to label the email simply “widget offer”, so as not to put off the red widget buyers.
This would be a mistake. “Blue widget offer” would get more blue widget buyers to open the email than a less specific subject line. And there’s no point in persuading the red widget buyers to open the email anyway. Don’t waste the red widget buyers’ time just to get your name in front of them, or (worse) just to get your open rates up.
Best of all, of course, would be to send the email only to the blue widget buyers in the first place.