Subject Lines: Rules + Best Practices

Ah, the ever-elusive subject line. Think of it as your headline before your headline.

After all, in a statistic from Convince & Convert with Jay Baer, “69% of email recipients report email as based solely on the subject line.”

That’s my focus.

You need to keep things clean and safe. Don’t get reported before people even have a chance to open your email!

There are many things to consider when thinking about subject lines.

“What am I trying to communicate?”

“How do I get them to open it?”

“How closely should it relate?”

Well, if you’re Joseph Sugarman, author of the Adweek Copywriting Handbook, you would tell yourself, “Oh, it doesn’t need to relate at all! It just needs to get their attention and keep them reading.” He had a very strict policy in copywriting that it doesn’t matter what your headlines say, it just needs to be big and lead the reader to the next thing.

I’m more of the school of thought that it should relate and be interesting.
Your subject line, to maximize opens, should follow 3 key rules:

Be personal

Be short

Be clear

In SEO, a key component Google looks for to help your blog rank is clarity in alt text (the text that describes pictures on your page) and meta text (the text that describes your page to their search engine). Why? Because they understand how important it is to be clear, concise, and easy to understand.

No one wants to go into your website or email with one expectation and then get completely thrown.

You’re more likely to convert if your reader gets what they expect and then some.

You’re less likely to convert if your reader expects one thing and then feels fooled when they open it.

Case Study Moment:

I worked with a direct marketing specialist who once had a 65% open rate on a list of 100,000+ because one day he tested the subject line: “Oops…”

65% open rate!
1.5% click thru rate…

The readers felt fooled. And this is not a criticism of his work, though I’m sure he’d appreciate me promoting his successes, because he tested and tested and learned there actually is middle ground to be had.

Subject Line Types:

Yes, you’ll argue with me. “Aren’t there more types?! What about questions or humorous?!”

My argument back to you: “They all fall under the following three subject line types. Also, calm down.”

Plus, this is from years of testing and studying. Trust me.


The curiosity-based subject line is probably the most effective. After all, it did kill the cat. (Not sure what I meant by that, but I’m not mad at it either.)
In an email from, after about 3 days of not converting with them, I got this email: “I don’t like this, but I’ll do it anyway…”

Yes, I clicked. They offered me a discount against their will. The subject set me up in many ways:

I felt empowered because they were conceding. It felt personal because I felt like I was being talked to. It made me very curious to what they were gonna do that they didn’t want to.

Curiosity-based emails are good for questions, including names, etc., such as: “Cup of coffee, Mike?”

I assume a coffee wholesaler or coffee shop with email list would want to send that one. If you’re taking this course and want to send a personalized email to your coffee shop’s email list…There you go. Don’t use “Mike” though, use their first name. We’ll talk about how soon.


“Today only”

“Don’t miss out!”

“Buy this, or else.”

Time = fear. Your customers or readers feel like they’re going to miss out will get them to act faster.

An effective email from Digital Marketer had a subject line that read “Your 7-figure plan goes bye-bye at midnight…”

A bit long, yes, and I would have tried to include the subscribers first name, but it has personality, it’s clear, and it has a sense of urgency.

Straight Forward.

The old “I’m your friend I promise” trick.

The straight forward subject line is simple, clear, friendly, as if you know the person.

We’ve all heard about President Barack Obama’s legendarily personable subject lines. My favorite?


That’s it. It’s in multiple articles and blogs online. Because it worked.
Why does it work? Because it feels like a friend sent it. And as a liberal myself, I like to think a friend did send it. 🙂

Other examples of Straight Forward subject lines:

“Hey man, did you see that?”

“I have some files for you”

“Remember that one time”

These are all characterized by lower case characters and most often, a lack of punctuation unless its a question.

Rules for Subject Lines:

Some basic rules for you to follow when writing subject lines.

Keep it UNDER 35 characters. Mobile apps usually cut your subject line off around 35-50 characters. If you’re including your subscribers first name, be sure to get the main point of the subject line in under 35 characters so they can at least get an inkling it’s personalized.

Stay away from NUMBERS. “Free” is a good word to use, but SPAM filters love to pick up on numbers and percentages. Typically, there are ways around them, but no need to get tangled in that web if you can avoid. The rule here is to keep your emails in their inbox.

Always TEST your subject lines. Always test and resend the winners to non-openers. More on that later, but write that down. ALWAYS TEST. A/B/C, even D, test that subject line.


I talk a lot about “personalizing” emails. But what does that mean?

ESPs will often have a field that, if included in your email, will include your subscriber’s first name in the subject line (and body too) of the email. All you have to do is include it in the field.

In ConvertKit, an ESP for creators and entrepreneurs, it looks something like this:

Subject line field in ConvertKit

This will only work if you got their first name when you onboarded them.

That’s why on my list builders, I always ask for their first name. Of if you’ve effectively gotten their permission when they checked out, your ecommerce company should have plenty of data you can merge into your email.
Other ways to personalize?

eCommerce companies, pay attention: You can merge your customer’s location data with your ESP, I promise. Just make sure the integration is advanced enough to take it. If not, you can contact your ESP and they will give you the tools to import a properly formatted CSV.

Now you can put “Los Angeles” or “Atlanta” or even target emails by zip code! True story.

Preview Text

What is preview text?


Examples of Preview Text in emails

For Petco, the preview text is: “Celebrate National Cuddle Up Day with…”

For BottleKeeper: “BottleKeeper 2.0s are back. Only for a limited time…”

Why does this matter? It’s EXTRA subject line space!

Not every app will display it, such as mobile, but when it does, it gives you extra space.

Some ESPs have a specific field for your preview text that will hide it from your email body. Others do not and will require you to get clever and integrate it into the top of your email.

I prefer the latter, it keeps things fun. For example, in ConvertKit, I can include preview text like so…

Where to input/how to deal with preview text when creating a campaign.

See how I made it smaller than the rest of the email, to make it clear it’s part of the pre-amble, and out of the way?

And if you want to avoid the body of your email creeping into your pre-header, use Litmus’ subject line preview text hack that helps you get rid of all that extra text with a simple line of code and easy instructions. I use it and so should you. The Litmus hack will also hide your preview text completely.

Check it out here.

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