Newsletter #5 - The ultimate cheatsheet to generate high-open rate email subjects

Newsletter #5 - The ultimate cheatsheet to generate high-open rate email subjects

Julie Cauville

Julie Cauville

February 22, 2023

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In a marketing email, writing the subject line is probably the most important step.

The future of your campaign will depend on these few words: convert your leads into customers or end up in the spam folder.

To avoid the second option, let me share my cheat sheet with you so you can write subject lines that will send your open rates through the roof ⤵️

☑️ Keep it short

About 40% of your leads will open your emails on mobile. If your subject line is too long, it will be automatically cut and you may miss your goal: for your email to be read.

Therefore, it is better not to exceed 50 characters

To make sure that your subject line is visible on all media, I recommend that you always start by setting up your email on mobile before you do the same on a desktop!

Bonus tips to shorten your subject lines.
-> Delete adverbs, adjectives, pronouns and prepositions.
-> Replace sentences with one word.
-> Prioritise single-digit numbers over longer numbers (I’ll tell you more below)!

☑️ Provoke an emotion

If you want your recipients to click, you need to pique their curiosity.

To do so, there are keywords that give rise to 7 universal emotions:

  • Vanity: brilliant, sexy, awesome, unbeatable...
  • Laziness: guide, simple, in less than, child’s play...
  • Greed: enjoy, benefit, huge...
  • Urgency: don’t miss out on, more than…
  • Humour: funny, entertaining, original...
  • Trust: approved, tested, authentic, a lifetime...
  • Desire: for you, custom, unique...

Bonus: 17 words that naturally arouse curiosity
-> adjectives:
surprising, strange, limited, overview, unknown, confidential, forbidden, unprecedented, private...
-> verbs:
discover, unveil, reveal...
-> nouns:
secret, invitation, confession...
-> expressions:
behind the scenes, hidden side...


☑️ Don’t be afraid of humour!

Like yours, your leads’ inboxes are flooded with emails every day.

Using humour is a great way to stand out (and to improve your personal branding, by the way)!

PS: brands that sell using humour know their target audience inside out, so I recommend you segment your lists before you start.

How to achieve +30% sales through email.

To help you increase your turnover quickly, I'm sharing Bigblue and Wisepop's free playbook to learn how to segment your target audience and build an effective email marketing strategy for your e-commerce ⤵️

Access the playbook for free

☑️ Use numbers

It’s science, the human brain is naturally attracted to numbers, partly because they help us organise information in a logical way.

There is even talk of "brain candy" 🍭

3 fun facts on the use of numbers in marketing.
-> Small numbers (digits) are easier for the audience to get their head around,
-> Odd numbers are perceived as more authentic than even numbers,
-> Even numbers make it easier to retain information.

☑️ Speak the same language

If you had to remember just one rule about subject lines, let it be this: always talk to human beings.

When you write your subject line, ask yourself "Would I like to read this?" and you will quickly identify superfluous words.

PS: applied to the subject lines of all your marketing emails (and even to your overall strategy), this concept is a great way to improve your customer experience!

For example, in your follow-up emails:
✅ "Your order is on its way!"
❌ "Order n°438643763 is being processed"

Maintain a good relationship with your clients, even after payment!

To give your customers a memorable experience and increase your Net Promoter Score (NPS), personalise your post-purchase emails like those of OMA&ME!
Know more

☑️ All caps and exclamation marks should be banned

Subjects lines such as "OPEN FAST AND GET A FREE TRIAL" or "50% discount for 24h only!!!!!!!! will not help you improve your open rate.

Your mail will probably be ignored, or worse... it will end up in the spam folder!

All you will have managed to do is to lower your Sender Score.

What’s the Sender Score?

A score between 0 and 100 (>70 is considered bad), it defines your reliability as a sender based on the behavior of your recipients (spamming, number of unsubscriptions, etc.). You can calculate it for free on

☑️ Remain human

The secret to getting a place in your leads’ inboxes: become their best friend.

The first step is to humanise your “from” name (see your email address, for example:, even if your email is automatically sent from a generic address.

Unbottled sends their marketing emails using Sarah’s name, their founder.  ⤵️

PS: Don't worry, I’m not a robot 🤖

☑️ Use emojis

56% of brands that use emojis in their subject lines have better open rates.

This is not surprising since they allow to:

  • Easily convey an emotion or idea (ideal when you run out of space),
  • Stand out in your recipients’ inboxes
  • Remember a message more easily.

3 fun facts about emojis in marketing
🧔🏻♂️ Men are more likely to view emojis as having no place in a brand’s communications,
👧🏼 Those aged 25 to 44 year are the most favourable to emojis,
🥇 There is a
Hubspot ranking of emojis with the best open rates ⤵️

Thanks a lot for reading so far!

I hope you enjoyed this newsletter.

See you next week!