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Every email marketer on the planet knows the importance of a subject line. But what really makes a great one? Believe me, if I had the holy grail of subject lines then I’d be a rich man. Sadly (and much to the chagrin of my wife’s wardrobe) I’m not.

Last week I delivered a presentation at Figaro Digital, a collective of thought leading digital marketers who meet semi-frequently to discuss all things digital. You can view my presentation and my beard here.

Afterwards, a gentleman came to speak to me and he asked me point blank, “What’s the best subject line ever?” I did my best to change the subject to no avail.

This is a question I’ve been asked many times before, and I’m sure I’ll be asked many times in the future. My answer often underwhelms, however it’s the absolute truth.

Now, before I go into what the answer is, a bit of a caveat. When I was working client-side, I knew what the best subject lines were. But my definition of “best” was very specific. The dictionary says:


But in an email marketing context, none of these are quite right. What people really mean when they are looking for the “best” subject line is the one that works better than all the others. It is fundamentally impossible to know which is the “best”,  short of running a campaign with infinite splits; testing out all possible permutations of subject lines, from the mundane (“Here is your email”), right through to dangerously spammy (“Get free Viagra delivered by Britney Spears now!”)

So, the way I interpret the question is as follows:

“What subject line will deliver my business the most value, given the constraints and nuances of my industry?”

But, that’s a bit of a mouthful, so most people just ask what the best subject line is.

And my answer?

“The best subject line is the one that works the best for you.”

Yep, as you can guess, this underwhelms people. Perhaps they are expecting a magical silver bullet that will suddenly make their email campaigns double in effectiveness. However, these successes are fleeting.

From a game theoretic standpoint, once one player in an industry finds a lucrative subject line strategy, competitors will mimic it, thus levelling the playing field and taking the global results to the previous equilibrium level. Therefore, short-term wins in terms of subject lines will deliver short term benefit, but in the long run will deliver nothing but wild response variance and thus a very stressed out marketer.

The key is to focus on building up your digital brand, and your subject line is a key conduit in doing so.

The best subject line should be:

  1. To the point. Don’t faff about – let people know why they should open the email. Don’t bait and switch; digital consumers value honesty, with the litany of untrustworthy advice on the web.
  2. On brand. When people trust your brand (see point #1) they will be more apt to open and read your emails on a regular basis.
  3. Call to action. People get many emails every day and don’t have a whole lot of time to spend on each one. Let them know the direct benefit(s) of opening your email and they will!

There is much more to optimal subject line selection – right from word choice, to length, even to inclusion of symbols and old, previously-perceived “spammy” words which no longer seem to be.

If you’d like to learn more about this topic then get in touch with your account manager. Just don’t ask us what the “best” subject line is because we’ll change the subject!