The evolution of human testicles – and other great email subject lines

If your email doesn’t get opened, it hardly matters if it’s full of clever copy, gorgeous images and a killer CTA.

Here at Sticky, we’re fascinated by email subject lines and all their power and potential. Are you as curious as us?

Humans are busy and inboxes are bursting but, once in a while, a subject line comes along that’s so compelling you just can’t help opening the email. But how do some brands get it so right and others oh-so wrong?

With professionals receiving an average of 121 emails a day, how do you stand out in a crowded inbox and get your email opened?

1. Don’t rush the process

Your email subject line has a huge impact on your open rates, and we think it needs as much, if not more, consideration as the content of your email. If your email doesn’t get opened, it hardly matters if it’s full of clever copy, gorgeous images and a killer CTA.

In short, do not rush this step. It pays to take time to hone your subject line until it’s the right length with the right combination of words – and emojis if your brand uses them. (If you do, a maximum of one emoji is recommended.)

I like to email myself a range of different options for subject lines and see what looks ‘best’ in my inbox (including on my mobile), when in-situ, surrounded by other email subject lines crying for attention.

2. Think reader-first

My first piece of advice for creating a good email subject line is to get out of your own head. You may have been tasked with creating your brand’s July newsletter, but your customers don’t know that and nor do they care.

A reminder that three million emails are sent per second. Therefore, please don’t call your email “Our June newsletter”. Your customers have no idea how often your emails come or whether you forgot to send the May newsletter.

Here are some examples of subject lines that are too inward-facing:

This one from JustPark assumes I’m interested in who their CEO is and that I have time to open this email and see what it’s about.

In this scenario, I would advise the company to avoid using the CEO’s name (unless they’re famous) and to explain what the email is about in the subject line and pre-header, so I can choose whether to open it or not. If you’re delivering a corporate message, with no call to action or next step, try to deliver it within the subject line and pre-header if you can.

Hamish from Heal’s

A message from our CEO

The same applies to this email from Heal’s. I don’t have time for ‘enticing’ subject lines. When I did open the email, I discovered it was about the Heal’s summer sale. That would have been much better use of the subject line.

3. Vibe with your pre-header

The key to a great pre-header, or preview text, is to build on the subject line not repeat it – that’s a waste of prime real estate. Your subject line is designed to stop the scan reader in their tracks and your pre-header gives them the final nudge to open the email.

Your pre-header can also work to give more factual or descriptive information if you’ve gone for more of a teaser subject line. Whatever you do, don’t leave this blank when creating your email, or your customer might see yucky default text like: “Read this email in your browser”.

Here are some examples of when the partnership between subject line and preview text works juuuuuuust right:

NARS Cosmetics UK

Correct. Contour. Highlight.
This iconic concealer does it all.

BETTER

Bring a friend for FREE* at Lee Valley White Water Centre 🌊
Double the thrill, half the price – White Water Rafting Awaits!

Champneys

Reminder: you’re due a day off
£99 spa day for your soul

As of December 2024, Apple Mail – who have the largest market share of users – replaced pre-headers with AI-generated summaries based on the content of the email. However, you should continue to use pre-headers for other email providers such as Gmail.

4. Be vocative (sparingly)

Once a hackneyed trick to get email opens, throwing in a first name is not as common now. Used sparingly, it’s a quick way to stand out from the inbox competition.

Ocado and LES MILLS+ do it well:

Ocado

Claire, get ready for your Easter feast
Smashing food and drink, plus plenty of recipes

LES MILLS+

Claire, your Pilates era is here
8-week plan: Feel stronger, calmer, better

Note, they also use action-orientated verbs like ‘get’ and ‘feel’.

ManyPets pet insurance on the other hand, goes too far with the use of names:

ManyPets

🐾 Paws up for free doggy ice cream at Bill’s, Nancy!

Confusingly, they aim the email subject line directly at my dog which gives me the ick slightly. And they don’t consistently use her name in the body of the email – they use mine too – so it’s additional cognitive load. They also sometimes send emails addressed to me, not the dog, so it’s not a consistent brand decision.

Maybe it’s my fault for giving my dog a human name…

5. Keep to your brand tone of voice

Subject lines need to follow your brand tone of voice too. Even when delivering difficult messages, you don’t need to veer completely off your TOV.

I thought this was pretty corporate and robotic from Vans shoes:

VANS

Information About Data Incident
We are writing to inform you about a recent…

6. Praise the half-pipe

Heaven is a half-pipe when it’s used to showcase multiple segments in an email, particularly if each content section appeals to a different audience.

Which? tends to do this really well:

Which?

NI cuts vs the state pension | Silly supermarket subs | Isa investing tips

However, it’s worth noting that the end of this subject line would be cut off when reading it on mobile.

According to Mailchimp, the current subject line length recommendation is no more than nine words, or 60 characters.

7. Build trust

If you build trust throughout your relationship with a subscriber, and respect their inbox, in time you may be forgiven for small mistakes or sub-par subject lines. We all have a couple of brands who can do no wrong, and we’ll always open their emails – but these are extremely rare.

8. A/B testing for the win

Testing subject lines is a low-cost no-brainer. You can also use your recent email stats to see what’s been working well for you in terms of open rates. Here at Sticky, we recently had impressive open rates for:

From logic to emotion in B2B: Your buyers are human too! (47.6%)

93% of marketers can’t be wrong? (49.1%)

And finally, our personal favourite email subject lines

Here are some of our favourite subject lines of recent times. These have all caused us to stop the inbox scroll-of-doom and click through for a guaranteed interesting, useful or funny read:

The evolution of human testicles (The Conversation)

A very good reason not to support the Guardian (The Guardian)

Why we’re selling illegal heaters (Which?)

We like big butts and we cannot lie (Who Gives A Crap)

We have aircon 🥲 Plus Lina Scheynius, Zoe Dubno, David Wojnarowicz (Pages of Hackney, bookshop)

Of course, I’m a Novelty Explorer®, so these would work well for me, as they’re either timely and topical (aircon in a heatwave – this email wasn’t pre-written and pre-scheduled!) or they do something different; they flip the genre on its head. But what about the other Curious Consumer Cohorts®, I wonder? Clarity Seekers®, for example, possibly don’t like puns in their subject lines as they prefer things to be as clear as possible.

For support with your emails subject lines, from one-off emails to whole campaigns, including onboarding, get in touch with Sticky.