The Most Important Part of Your Email Isn't What You Think

Jun 26
3 min read

I've written thousands of marketing emails over the course of my career. Some generated exceptional open rates, clicks, leads, and sales. Some didn't.

One lesson has remained constant.

The most important part of your email isn't the design. It isn't the copy. It isn't the message. It isn't the call to action.

It's the subject line.

The subject line is the only part of your email every recipient will see before deciding whether to open it… or delete it.

Don't overlook your preheader. Too often, it's left blank.

Your preheader should support your subject line, not duplicate it. Think of the subject line as the headline. The preheader is the supporting sentence that reinforces the promise and gives someone one more reason to open your email.

Years ago, I worked with a client who cared deeply about every email we sent. We'd spend hours refining the message, discussing the audience, and polishing every paragraph.

By the time we finished, we'd sometimes invested hours refining the email. Yet we'd spend just a few minutes on the subject line.

Looking back, we had it backward.

We were investing most of our time perfecting the part many people would never see.

That experience changed the way I think about subject lines.

Over the years, I've learned not to settle on the first subject line that comes to mind. I write several. Some are straightforward. Others focus on a benefit. Some create curiosity. Others simply promise to solve a problem. Then I test them.

One of my favorite ways to test subject lines is with AI. I'll tell it who the audience is, what I want the email to accomplish, and provide several subject line options.

Sometimes AI writes a better subject line than I do.

Sometimes it takes one of my ideas and makes it stronger.

Other times I challenge its recommendations, and it asks a question that makes me rethink my approach.

I don't always take its advice, but I almost always learn something from the conversation.

I've also learned that the best subject line depends on who's reading it. An operations manager and a CEO may receive the same email, but they often care about different things. An operations manager may be focused on efficiency, saving time, or helping their team be more productive. A CEO may be thinking about growth, competitive advantage, or reducing risk. The email itself may not need to change. Sometimes the subject line does.

If an email doesn't perform the way I expected, I don't automatically assume the message failed. Sometimes the subject line simply wasn't communicating the value in a way that resonated with the audience.

Most email platforms – including affordable ones like Constant Contact and Mailchimp – let you resend a campaign to people who didn't open it the first time. I almost always use that feature, but I never use the same subject line.

I'm often surprised by how many people open it the second time. Was it because I sent it on a different day or at a different time? Maybe.

More often than not, I think the second subject line communicated the value in a way that resonated with the audience.

That second send also teaches me something. Who opened it? Who didn't? Did operations managers respond differently than CEOs? Did one audience segment find value while another ignored it? Every campaign is another opportunity to better understand your audience.

One word of caution, though. Just because you can resend an email doesn't mean you should keep sending it. I typically resend it once. After that, I move on. If someone isn't interested, repeatedly showing up in their inbox won't change their mind. It only increases the chances they'll unsubscribe – or worse, mark your email as spam. The goal isn't to squeeze one more open out of every contact. The goal is to build trust.

I also keep a folder of emails that catch my attention. Not because I want to copy them, but because I want to understand why I opened them. What made me stop scrolling? What promise did the subject line make? Why did it work?

After thousands of emails, one lesson has never changed.