Though we do want to keep a short subject line, a short subject line is useless if it fails to convey your message. Richard Lindner of Digital Marketer says, “A shorter subject line will never overcome poor messaging.”

Richard also talks about the “second” subject line, or the “preview.” He adds, “Don’t forget about the second subject line, or preview description. In most cases you have more characters and the ability to personalize or add more copy for your subscribers, telling them why they should open your mail. This is the most under-utilized and ignored portion of almost every email marketer’s assets.”

The preview is the small bit of copy that offers a sneak preview into your content. Most email platforms allow you to customize that preview. Richard gives a great example of what that can look like.

People think in terms of keywords more now than they used to. Having one or two keywords in the subject line is a great way to quickly show value and relevance to your audience. However, keywords in subject lines offers another great benefit, and that’s the ability to search for your emails more easily.

Most users hold onto emails, particularly in content heavy industries where emails act as a sort of information archive. For example, if I want to see what the email conversation was for the last five years on a certain subject, say for example “Summer,” then I can just search for that keyword and all the email marketing campaigns with the subject line “Summer” will pop up. Better yet, if a certain email marketing campaign has religiously been keyword-oriented, then their subject lines will offer quick points of reference to various summer campaigns, events, sales, initiatives and more. For example, I can run an email search for the keyword “Foreign students.”

Of course, using a keyword in a subject line doesn’t need to be boring. You can still optimize that copy to make it more friendly, more casual, or creative in some other way; you just need to get that keyword in there once.

So the next question is … exactly how long should your subject line be?

According to a Digital Marketer blog post on the ideal length of a post, email subject lines should be between 28-39 characters. Here’s why: “subject lines containing 28-39 characters get an open rate of 12.2% and click rate of 4% on average. You should also factor in that with most people being on mobile, shorter characters is even more critical. Lindner reminds us, “Mobile has WAY fewer characters. Focus on your message and you’ll get the open.”