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What Makes Good Subject and Preview Lines in Email Marketing?

#5 in Our 20 for 20 Series

Welcome to 20 for 20 where we share our 20 best tips for email marketing and business to celebrate our 20th Anniversary.

First, we have some bad news about subject lines. They are NOT the most important thing that determines whether or not your email gets opened. As we explained in our last video, it’s your “From” name. What I really mean by that is, it’s your reputation for providing value that’s the most important factor—and changing your reputation can take time. But the subject and preview lines are next in the order of importance, and that’s what we’ll cover today.

Before we do that, I have MORE bad news. Not even with my 20 years of experience can I, or anyone else on the internet, give YOU the silver bullet answers on how to write subject lines. So don’t believe anyone who says they can. The data is always changing and your relationship with your audience is so unique that you can’t take any of these tips as gospel.

There is good news—there are some best practices and ways to think about subject lines that will help. So, big picture… Think of the subject line like the title of a book—it has to create the desire for someone to read it. People want a way to sort their mail and are deciding whether your email is worthy of their attention.

The question becomes “how do I get their attention with so little real estate?” First, there are several categories you can put subject lines into. In general, we use a subject line to pique curiosity or convey value. It could be informative or intriguing—most importantly, it has to grab your attention.

Successful subject lines communicate one of the following (per Ryan Deis, author and leading digital marketer):

  • Direct benefit:The 5 Biggest Email Marketing Mistakes That Almost All Businesses Make.” Or… “40% Off Storewide Now.” I remember when I was approving an email for one of our clients and our subject line was something like “Our Big Event.” Only after I’d opened it and read to the bottom did I see they were offering 40% off store wide—because the client didn’t want to sound “salesy.” Obviously we changed it. If there is an undeniable direct benefit to the reader—put that FIRST.
  • Curiosity: “What all the girls are talking about…”
  • Scarcity: “Only 3 Left in Stock”
  • Urgency: “Free Shipping Expires at Midnight”
  • News: “U.S. Successfully Stops Spread of Coronavirus”
  • Social proof: “Why Everyone Is Buying This Weighted Blanket”
  • A story: “How a Simple Farmer Became an Overnight Millionaire”
  • Humanity: “The 3 things I hate About Myself”

Hopefully this framework will give you some ideas for subject lines.

You can also help your subject lines stand out by using power words like these, and by watching the length. Too long and they’ll get cut off in inboxes. The optimal length is between 41–50 characters, however it varies across email clients and mobile users.

And you should break the rules once in a while. Try a really short or a really long subject line and see what happens. Be outstanding—which literally means stand out.

Mailchimp sends out billions of emails every year, and they’ve put together a best practice approach. Here are some do’s and don’ts.


  • Add personalization (not just the name, but other relevant data—more on this in a minute).
  • Be descriptive.
  • Use power words.
  • Keep it short.
  • Put the most important words first.
  • Limit punctuation.
  • Use emojis carefully.
  • Test subject lines (we’ll get to this in a future 20 for 20 video).


  • Use click bait. Make sure the subject line is relevant. Remember that reputation thing?
  • Use words that are known Spam triggers (check your subject line using this online tool).

Here’s an Email Broadcast exclusive (I haven’t seen anyone else talk about this practical tip). I force our team to write at least 10 subject lines for every email. It’s part of our process and it works. You think your first one is good, then you keep going and by number 7 you’re really getting dialed in. Try it.

Another advanced ninja move when it comes to subject lines is personalization and relevancy. The more targeted your audience segment, the more powerful your subject lines can be. Let’s say you sell vitamins and you know a portion of your audience is women—and not just women, but women who practice yoga. Your subject line targeting this segment could be: “Why Women Who Practice Yoga Need This Vitamin.” That’s a winner all day long.

Here’s a true story about using segmentation. One of our clients is a furniture retailer and we targeted a small segment of their list—people who had a private credit card (with good credit) and people who had a store credit account (with marginal credit). We created two different targeted emails for this small group—now only about 4% of the client’s list—with a subject line that was something like: “Good news Ken—we’ve extended your line of credit!” We drove $430K in sales in one weekend. Look for ways to target a smaller portion of your list with super relevant subject lines.

Before I talk about preview lines, I want to remind you that we’re giving away something for every 20 for 20 this year, and this month everyone’s a winner. I’m giving EVERYONE on our email list one of the coolest tools known to man—maybe as valuable as the wheel itself… the letter opener. Just click the link on the email you got so we can get your address, and we’ll send your new favorite tool absolutely free of charge. Because we know that email is not the only mail you open. Go ahead and see if we’re for real. Sorry we’re limiting this offer to US addresses only. If you’re on our email list but you’re not in the US, give us the name and address of someone who is and we’ll treat them on your behalf.

Now let’s talk about an often-ignored, but very important, aspect of email marketing—the preview line. What is it and why is the preview line important? It’s one of the key ways we tell if someone has their email marketing house in order, or if they’re still playing rookie ball. It’s VERY important. It’s the third most important piece of information, behind “From” name and subject line, that will help a reader decide whether to open your email.

Preview lines should always compliment or add to the subject line. The preview line acts as a continuation to provide additional information/expand on the email’s content or a call to action. It can also offer an additional benefit of opening the email that the subject line doesn’t address. NEVER let your preview line be “If you have problems viewing this email, please see the web version.” That’s a rookie mistake. NEVER repeat your subject line. We see that a lot too.

Where do you put the preview line? If you’re using a decent email service provider, there will be a designated place for the preview line. If you’re not, it will likely be the first line of your email. That’s why you see the dreaded “If you’re having problems reading this email…” as the preview line, because the template has it at the top.

OK, to wrap up, here’s your takeaway on subject lines: There’s no silver bullet, but you should follow some best practices that we outlined, including writing at least 10 of them. And always use the preview line in combination with your subject line.

In our next 20 for 20, I’m going to give you a giant gift—garnered from 30 years in business— that’s going to impact every aspect of your business and personal life. Make sure you don’t miss that one, and in the meantime, be sure to sign up for our 20 for 20 campaign if you haven’t done so already.

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