Jakob Nielson wrote a great article on email usability. There is a lot of good points but I wanted to focus on his section about subject lines. As a rule of thumb, if you have doubts on what the subject line should be . . . be direct.
There is a great example in the article of a subject line that the ad or marketing people probably loved. And with good reason, it’s a witty one liner. It just sucks as an email marketing subject line because it doesn’t give recipients a clue as to what the email is about.
In marketing and advertising it’s easy to be swayed by our cleverness. The problem is that almost all email recipients don’t have time for clever. They get too many communications to want to revel in advertising wit.
Make subject lines to the point and open rates will be better. Our testing typically shows a 10% – 20% decrease in opens if a question or tag line is used in the subject line vs. a direct subject line that summarizes the email content. The same is true for subject lines that are too long, so don’t attempt both direct and witty.
Tell recipients what you want to talk about. The email is the chance to tell them again with more detail. Finally the web landing page is a chance to tell them a third time and give them an opportunity to act on it.
It might not be flashy, but in email marketing the subject is your first chance to say something. Make sure it sets recipients up for the email’s content, not leave them guessing about what a clever subject line has to do with anything.