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Email marketing subject line do’s and don’ts


Ain’t that the truth?

For those of us in the email marketing field, who must compose dozens, hundreds, even thousands of subject lines over the course of our careers, “challenging” barely touches the sides of what we actually have to contend with.

Inbox filters, reader indifference, the ever-present army of spammers and scammers nipping at our heels every step of the way, and an increasingly sophisticated/discerning audience all converge on our largely misunderstood livelihood to make marketing email opens an increasingly rare commodity.

Overcoming such odds to get eyeballs on our emails and content is a big ask. A robust, healthy mailing list is a good first step, since, as many love to point out: in this game, sheer volume is tough to beat.

But simply sending more emails isn’t the answer to everything.

Massive mailing lists can be expensive and hard to come by. Emailing people too often can also damage a brand and increase churn rates.

And nobody wants that.

A much healthier solution is to look for ways to increase the percentage of emails opened, while still maintaining a healthy subscriber retention rate. That way we can generate more revenue AND keep our audience from labelling us spammers.

But how can we accomplish this?

Let’s ask Gandalf. He has usually got some good suggestions…

email subject lines Gandalf

What a wise old wizard he is!

When it comes to increasing open rates, subject lines are the key. That’s why there are so many blog posts written about how to write better ones, and why the list of adjectives used in such blog posts claiming to have all the answers is as long as it is inane:

  • “Eye-popping”
  • “Eye-catching”
  • “Effective”
  • “Amazing”
  • “Attention-grabbing”
  • “Sure-fire”
  • “Persuasive”
  • “Killer!”
  • “Enticing”
  • “Alluring”

And that is just from the past 24 hours.

All great adjectives, to be sure, but, in our world, it really only comes down to “effective” (meaning subject lines that increase opens), and “ineffective” (meaning subject lines that don’t).

Here at Phrasee, we have tested millions of subject lines in many different business sectors for many different companies over the past several years, and, while of course there are always many factors to consider, a few trends have emerged.

We have decided to share these trends in the form of a “dos and don’ts” list, since everyone loves lists.

You know what else everyone loves? Cats. So we’ve included those too.

Email marketing subject line do’s and don’ts (featuring cats!)

Do: Be clear


People are busy these days. The odds of an unclear subject line enticing someone to open it are slim at best. The people want to know what they are getting into if they open your email. If a recipient cannot determine what he/she will find when he/she opens your email by reading the subject line, they probably won’t open it.

Don’t: Be boring

Image credit: Disney


Whatever the message is that you want to convey in your subject line, don’t be boring about it. We live in entertaining times, and boredom has become completely unacceptable (just look at how many cat gifs we had to add to keep you reading this far!). Boring subject line = boring email, period. And who wants to open one of those?

Do: Be funny


If there is one thing the internet has taught us above anything else, it is that people like funny things. Be topical, be sarcastic, slip in a bad pun, poke fun at someone famous, poke fun at yourself and your brand. If you can deliver one of those things in your subject lines, you will not only get more opens, you will build your brand. But tread lightly, humour is tough. Know your audience and your brand’s tone of voice and joke accordingly.

Do: Make it interesting

Image credit: Paramount Pictures


We know, we know: wasn’t this already covered by “don’t be boring”? NO! The question that all those who receive your marketing email will be subconsciously asking themselves is: “Is opening this email worth the next 30 seconds of my time?” Such decisions are made in a split second of brain processing time, and will not be revisited. You’ve got one sentence to grab your reader’s attention (maybe two if you push it) make it count.

***NOTE*** the body copy of your email had better be interesting as well.

Don’t: Use openbait


Nobody likes spam. If you use openbait subject lines, you are spam. Everything you send in the future is spam, and your marketing emails are annoying forever. Mailing lists are notoriously unforgiving of such tactics. Just. Don’t.



Presumably there was a period in the history of email when there were only a few email marketers who were using all caps in their subject lines. Maybe their open rates were off the charts for a while. Maybe they really felt like they were on to something. However, those heady days are long behind us, and anyone using email marketing subject lines written completely with capital letters in an attempt to make them stand out in this day and age is clearly out of their depth. Welcome to spam town, population: you.

***NOTE*** once everyone finally stops using caps altogether, this tactic may experience a brief renaissance, but, will it be worth it?

Don’t: Overuse exclamation points!!!!!!!!!!!!


Sigh… exclamation points. They meant something once…

Do: Offer value


Cat spitting fireballs in space“… That subject line, coupled with the above gif in a marketing email’s body represents a successful email marketing transaction. For you: an open, for the recipient, a few seconds of pure joy. It’s win-win. Offering value really can be that simple. Everyone on your mailing list knows that your emails are pure marketing, designed to separate them from their money and nothing else. But that dialogue can be valuable for both parties, and this is when it is the most effective. Offering value in exchange for your reader’s time is only fair, really. And people love fair.

Don’t: Use off-brand lingo


Brands are not cool. Well, maybe a few are but they are extremely rare. Using lingo and buzzwords will not change that. A non-hip-hop brand using the latest hip-hop phrase is pretty much like your parents using it: just wrong. Don’t be that person.


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