The conversion rate of an email is heavily weighted by the subject line. Your prospects will look at the subject line for less than two seconds. That is about as much time as they get with a billboard on a highway. A subject has to intrigue your prospect enough that they’ll open the email. Without that intrigue, you just wasted all the time it took to write the email and put a mailing list together. Worse yet, maybe you just got unsubscribed. It is not unheard of for marketers to spend as much if not more time on the subject line than on the actual content of the email.