Ok, first off, we know you’re not a dummy.

But that doesn’t change the fact that crafting the perfect email subject line for an email marketing campaign can be surprisingly hard.

We totally get it, which is why we’ve been hard at work the past couple of years building Phrasee’s AI language optimisation software. Using Phrasee helps marketers make the most of AI-optimised email marketing language that both sounds like it were written by a human AND results in more opens, clicks and conversions. It’s pretty awesome.

That said, every email marketer (even those already using Phrasee) should still understand what’s involved in making great email subject lines.

The truth is, there are a LOT of different approaches which can perform very well for a particular brand, product, or campaign. That’s what makes split testing so important.

Unfortunately, there’s no sure-fire way to anticipate what kind of subject line will be the perfect fit before hitting “send”. What works for one company, product or campaign may not work for another. And, what works today won’t necessarily work tomorrow.

The good news is, once we abandon the ill-conceived notion that we can somehow solve the subject line puzzle using gut feel alone, we are left with plenty of room to experiment and test different tactics. Not only that, but we get the added bonus of being able to learn from the results and adjust our future subject lines accordingly.

Which is good, since although such testing/experimentation processes can be time-consuming, they are worth the effort. 

So, ready to become a subject line super hero? Let’s break it down.

The dummy’s guide to email subject lines

The dummy's guide to email subject lines

How a subject line works

For many of your subscribers, your email subject lines will more than likely be the only part of your emails they ever see.

This is why (combined with you sender name and the relationship you have developed with your subscribers) the subject line is your best chance to convince each subscriber to open your email and read your marketing message. You may have crafted the world’s best marketing email, filled with intriguing and highly relevant content, but all that work will be wasted if the subject line can’t get the recipient to open.

Think of it as a headline or blog post title, but with a touch more personalisation and the added threat that it could be deleted instantly or (worse yet) sent straight to the spam folder.   

How to split test subject lines

There are two different ways to split test the effectiveness of subject lines – A/B testing and multivariate testing.

Split testing can reveal how small changes in a subject line affect the open rates it generates. If a marketer wants to A/B split test their subject line, they’ll create two email campaigns that are exactly the same except for having different subject lines, then send the two different lines to different segments of their mailing list to see which one performs better. This helps them discern what types of subject lines, wordings and sentiments their audience responds best to.

Multivariate testing is even better, it’s asplit test that tests more than one variable at a time. Unfortunately, it generally requires a more substantial mailing list than A/B testing does.

In the case of email subject lines, different combinations of words, symbols (like emojis), and punctuation can affect the resulting sentiment contained within the subject line’s message, and thus how that subject line is perceived by its recipients.

Because of the large numbers of variables involved in any message (especially in English!), it is generally best practice to test for as many variations of a subject line as possible. The more variations tested the better!

Conveying the right sentiment

Language is more than just the words we use. It’s all about the meaning those words convey. The same holds true for subject lines. When we read a sentence, we don’t really read word by word and figure out the meaning as we go along. Instead, we read the entire sentence then subconsciously process it and its meaning, or sentiment.

Phrasee uses artificial intelligence to identify, create and quantify what makes your customers respond to your messaging. Through language algorithms and natural language generation technology, Phrasee figures out the sentiments your customers connect with and helps you write the perfect copy to get those sentiments just right.

Subject line best practices

Do:

Stay on brand

You’ve invested a lot of time and money building your brand and its unique voice. Are you going to throw that all away trying to get an email opened? You shouldn’t. Your brand’s voice matters and this simple fact does not change once you start writing an email subject line. Make sure that your subject lines are on brand, or brand damage becomes a very real possibility.

Be clear and concise

Subject lines are not the time to wax poetic about your product’s many attributes. They should be clever but clear enough that your recipient doesn’t have to guess at what the body of the email contains. Let people know what they’re getting when they click open as clearly as possible.

Personalise

When you’re sending out multiple campaigns to thousands of subscribers, it’s easy to fall into the mindset of viewing your audience as a group and not as individuals. Targeting specific segments of your mailing list is key to personalisation. It’s also a smart idea to write your copy with a single, key target in mind. How would you speak to a potential customer in real life? Use that voice!

Stand out

If your subject line follows the tips above, it’s sure to start standing out from the mass of other emails flooding people’s inboxes, but there are still more ways to play around. Testing the waters with emojis, humour, or pop-culture references is also an option, so long as it fits with your brand voice.

Optimise on the fly

In the digital age, things change quickly. A subject line which performs beautifully today could be completely ignored tomorrow. That’s why it is so important to keep on testing. Track your performance data as often as possible and make adjustments when things aren’t working.

What not to do

We know we said there’s no clear right or wrong way to do email subject lines, but there are a couple practices that can hurt you

Don’t…

Believe that what worked yesterday will work today

Modern tastes change fast, and brands need to stay nimble to survive. Keep an eye on your email performance metrics, and don’t forget to keep split testing. Writing the same (or similar) email subject lines for your marketing emails will soon make you look spammy and boring. In the email marketing space, spammy and boring do not convert.

Copy what your competitors are doing

Standing out in a crowded inbox can’t be accomplished by copying the competition. Only unique, interesting subject lines will get you the opens you crave. Be original!

Make false promises

Making a false promise in your subject line – saying one thing but actually have the bulk of the email be about another – is poor practice and will quickly get your readers to click ‘unsubscribe’. This can also be called “openbait”. Similar to clickbait (you know the article titles we’re talking about), open bait is an enticing subject line that effectively gets readers to open your email just to find out your message has nothing to do with the subject.

While using these tactics make work in the short run to increase open rates, they’ll soon annoy your audience and threaten their trust, ending up resulting in fewer opens and conversions.  

Use spam words

Earn extra cash! Make money at home! Buy direct! Score with babes! These are the types of phrases spam filters instantly hone in on. While spam filters can be triggered by more than just your email subject line, it’s important to keep in mind what vocabulary you’re using.

It’s pretty simple – don’t make your email subject lines sound like a sales pitch from a 90’s infomercial and don’t promise easy money.

We know that this all probably sounds like quite a tall order, and it is! Keeping a brand’s subject lines on point is a big job. This is especially true for brands with big mailing lists which send out marketing emails at scale. For a job this size, getting some help can make all the difference in the world.

That’s why Phrasee is here.

Drop us a line to find out how we can help!

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