Ecommerce email subject lines:
12 Best Practices to increase open Rates

Why effective ecommerce email subject lines can make or break your email marketing campaign

“On the average, five times as many people read the headline as read the body copy. When you have written your headline, you have spent eighty cents out of your dollar.” – David Ogilvy: Widely regarded as the father of modern direct response marketing 


This not only applies to email marketing, but all forms of copy and direct response marketing, when a user looks at your headline. They make a split second decision based purely on the several words of copy whether or not you’re worth their precious time.

Your emails could be fantastic, your flows the best in the world, but if your headline sucks then as Ogilvy puts it, 80 cents our of your advertising dollar is wasted.


A client of ours, an accountant was using the same sort of email subject lines everyone else does:

  • Trusted by locals
  • Increase your profits
  • You are losing thousands in fees

While these are all valid points and can be great headlines on their own what if everyone else is using them, so we experimented with more personal copy, something customers may identify with on a more personal level.

Both of these headlines performed significantly better and resulted in increased conversions, we’ll show you the ecommerce email subject line tips below.

How long should ecommerce email subject lines be?

There is no hard and fast rule for how long email subject lines should be, the only hard and fast rule is that it has to be visible!

Your email subject line needs to look clear, concise and can’t extend too far so that Email Service Providers (ESP) begin to cut it, it looks both unprofessional and people can’t read your subject line, and according to Ogilvy you’ve just blown 80% of your budget.

Subject line length will also vary greatly depending on the type of email, whether it’s a flow, campaign, uses any tagging e.g. names from your email lists as well as your business, if your tone of voice for your brand dictates a slightly longer subject line then you must be consistent.

Just make sure it’s visible to all users, you can check this when you test.

Email subject line too long
Email Subject line with the right amount of words

How to test ecommerce email subject lines for flows and automations

Testing is one of the most important factors to an ecommerce email marketing campaign, if you don’t test then you’re flying blind.

If your flows/automations don’t work, you’ll only find out once your results go through the floor.

Test, test and if in doubt, test some more!

A/B Testing your flows/automations at every possible opportunity is the key to maximising your open rates for your flows.

We use Klaviyo, this makes A/B testing relatively straightforward, as per the below screenshot, you can see that there are two variations of the second Abandon Cart email. We’ve blocked out sensitive info about our client but all relevant info remainse

Klaviyo split testing email subject lines

How to test email subject lines for campaigns

For campaigns, to test A/B test a campaign, it’s relatively simple in Klaviyo, you simply create a variation of the campaign email and then test which performed better, this is pretty straightforward. 

Where proper planning needs to be conducted is the reasons/theory/motivation behind the testing, what exactly are you testing in the headline? How will this be useful for future campaigns.

You need a valid hypothesis to test, some questions you need to ask yourself in this case are:

  • Are you appealing to emotion or logic? If emotion, what emotions? This is core to their motivations and needs to match your brand’s ethos
  • What key desire are your product/service targeting? Health, relationships or wealth?

Creating an email subject line for ecommerce

You can see here that we’re testing a minor variation of the headline for a supplements business all that’s left is to wait for Klaviyo to declare a winner, if you want to decide before then. Simply wait until either:

  • One is a clear winner
  • There’s enough statistical evidence to calculate a winner with confidence.

You can test just about any element of an email, but subject lines are the focus here.

Use of emojis in subject lines in ecommerce campaigns

The year is 2020, so here we are discussing emojis in the context of ecommerce email subject lines.

In short, yes! Emojis have many benefits for subject lines including:

  • Making your subject lines stand out, most people don’t use them as there’s still a stigma
  • Convey personality for your brand: you have only several words to convey your message as well as to generate intrigue. Emojis can significantly help with that.

However, there are several factors you need to consider to decide whether using an emoji in your emails is right for your brand.

Tone of Voice

Your brand’s tone of voice is integral to the success of not only using emojis in subject lines, but also your entire marketing strategy.

Is your brand bubbly in the way it talks to customers? Or is it more serious? This also depends on the very nature of your business.

If you market to gen y and gen z for example, as well as sell more hobby based, or fun products then using emojis would be a good item to A/B test.

If you’re tone of voice is more serious, or you offer a more utility base product or service then it would probably not be recommended to use emojis in your email subject lines as you want to convey a more serious tone in order to convey authority

Emojis in an email subject line

Target Audience

As mentioned, the use of emojis is also highly dependant on your target audience, what works for younger audience such as Gen Y & Z will not work for older audiences, although if your product/service is the right fit, it may still be worth A/B testing.

Email marketing is not engineering, there’s no specific equations or hard and fast rules, if in doubt TEST

Casing for Email subject lines

Lower case, all capital letters, title case, sentence case what option is best?

As with all other points here, choosing a case for your subject line depends on several factors including

  • The ethos of your brand
  • What your product/service is
  • What’s your target audience?

Exploring all three formats

Full Capital Letters

WHY ARE YOU YELLING AT ME? Is definitely a thought everyone has had when they receive a message from someone who has accidentally left their keyboard on all caps.

It looks spammy, unprofessional and is general just affronting to people, this is the only type that we can comprehensively say is not advisable, however as with anything it’s possible to split test.

an email subject line all capital case

Sentence Case

Sentence case is best for informal language or a more conversational tone. If you’re brand is more casual with your customers then this may be the way to go, especially for flows.

Sentence case has increased in popularity over recent years, many experts believe this may be due to the changing way we use the internet, especially in the context of asking questions and search engines.

As an example:

  • 10 years ago, you searched Google by “Cafes Sydney”
  • Today, you search “coffee near me”

The entire internet has become more conversation like and humanised to an extent as the it becomes increasingly part of our day to day live.

all lower case email subject line

Title Case

Title case is the most traditional and formal, if you’re providing a more serious service, then this may be the best method for your email subject lines.

Sentence case email subject line

This may also depend on your target audience and who comprises your email list, if your list is older then this may be the way to go.

As an example, a client we have is an accounting firm which specialises in hospitality, to start being conversational with our target audience would be a mistake as the goal here it to convey as much professionalism and authority as possible.

So what does this all mean?

This means there’s no hard and fast rules when it comes to your eommerce email subject lines. Besides obvious mistakes such as mismatching tone of voice to your brand, everything else is up to A/B Testing to determine.