How to Write Killer Email Subject Lines

If there’s one thing that marketers can agree on, it’s this: if no one opens your emails, then the content inside (no matter how brilliant) isn’t serving its purpose.

Harsh? Maybe.

True? Absolutely!

In this digital age, we’ve probably all sent email subject lines before that were not so stellar. (One of my own shining moments involved sending a professor an email with the subject line, “Um, help?”—Sorry, Dr. Fullerton!) Half the battle is getting people to open your emails to begin with, but how do you craft the perfect email subject?

It’s pretty simple: start by thinking back to the emails YOU are opening! Are the subject lines kitchy and catchy? Do they include emojis? Utilize personalization? Pay attention to what’s enticing you to open and ask yourself when writing, “Would I open this just by looking at the subject line?”

Now that the wheels of creativity are starting to turn, here are three tips for writing killer email subject lines:

Keep it casual

Let’s face it: the times we actually look forward to a formal email are few and far between. (Looking at you, direct deposit notice!) Although marketers can’t always expect to be as joy-inducing as a much-awaited Amazon tracking number confirmation, keeping a light and casual tone promises that something fun awaits, and that’s basically the next best thing.

For example, instead of writing, “Hello, Mr. ______,” try saying, “Hi there!” Even utilizing the “first name” personalization option that HubSpot offers is a great way to keep it casual. HubSpot also recommends using colloquial phrases for this technique. If you’re not sure how to “speak like the youngin’s” (as my grandmother would say), check out this how-to guide!


Use active voice

What do we mean by “active voice?” The short and sweet answer is this:

  • Active voice – When the subject of a sentence performs the verb’s action
    • Example: Kelly loves Starbucks.
  • Passive voice – when the subject is acted on by the verb
    • Example: Starbucks is loved by Kelly.

While both are grammatically correct, the active voice version is much more compelling and concise. Keeping a strong, confident tone is important for making people excited to open your emails (because really, who wants to read marketing emails that come off as timid and unsure…?).

Pro tip: you can almost always tell a sentence is in the passive voice when you see the above “’by’—noun” pattern.


Make it interesting

Remember, these emails are for people outside your inner circle and office cohort. We want people to engage with your content, not ignore your forwarded “Mercury is in retrograde!” email (which, by the way, should never be ignored: save all of your passwords and files now, people!).

Some of my own favorite subject lines are ones that people can relate to. If you’re writing about a new recipe, pique your audience’s interest by writing a subject line that’s related to the recipe. For example, a smoothie recipe subject line could be, “Save time on your morning routine with this recipe hack!” This way, the consumer could be thinking, “What recipe hack? Let me open and find out.” If you give away the whole email’s contents in the subject line, what reason do people have to actually click?

One of my mother’s (and probably everyone else’s mother’s, too) favorite dating tips is to “be mysterious.” While the world of marketing (thankfully) isn’t akin to a dating app, the message of “making people wonder” is certainly effective in this sphere. And hey, even if the subject line material can’t be relatable, then at least keep it interesting.

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