Last month Salon.com switched away from using "Salon Daily Newsletter" as the subject line of its emails. Now, such subjects lines as "Salon Daily: The 10 most compelling on-screen gangsters" show up in my email inbox.
Think about it. Which type of subject line would most likely inspire you to open an email? An unopened and unread email is like no email at all. Worse, in fact. An unopened email is an unwanted email with your name on it. An unwanted email is inbox clutter, and very likely it will soon be deleted.
A good email subject line gives the recipient a reason to open and read the email. From a marketing point of view, that is its main function, but the subject line must also accurately identify the content of the email. People do not like being tricked.