We all have ‘unread’ emails in our inbox. How many do you have? 100? 200? Or, if you’re like me and on countless email lists – 441?  

We receive TONS of emails every single day. In 2020, over 306 billion emails were sent/received daily worldwide. By 2025, the number is expected to increase to over 376 billion. The chances YOUR email will be ignored are quite high unless you know how to craft the best email subject lines fitting all the different email campaigns you’ll send.


“Email subject lines are like movie trailers. They give readers a preview of what’s waiting for them once they open your email.”  – EmailOut 

Do you know that 47% of recipients open emails based on the subject line alone? How about the fact that 69% of recipients will report an email as SPAM solely based on the subject line? Your email subject lines are the first – and possibly last – impression you can make on your target audience. Hence, you need to make sure they are perfect.

This article covers the following topics on email campaign subject lines:

  1. The connection between your subject line and preheader
  2. How powerful is a good email subject line?
  3. How to write the best email subject lines?
  4. Email subject lines best practice
  5. Email subject lines stats

Let’s dive in.

In many ways, email subject lines are even more important than the email copy. Why? Because your awesome email campaign is worthless if it never sees the light of day by being opened. That’s why it all starts with the subject line.

The Email Subject Line & The Preheader 

We all know what an email subject line is but what about that line of text shown next to (or under) the subject line? That’s known as an email preheader. It’s completely different from the subject line but the two are joined at the hip. They work together to convince your target audience to open and engage with your email campaign.

Be careful though. Your email subject line and preheader will be displayed differently depending on the device your recipients use to view their inbox. If you’ve neglected to ensure both elements make sense when put together, you may end up sending some peculiar, occasionally inappropriate but at times funny emails like Acme Toys and  ZURB University.

Your preheader’s purpose is to build on the subject line, not parrot it. Thus, being repetitive is frankly an ineffective and, to be honest, lazy technique. At the same time, you also need to be consistent. If your preheader goes off in a completely different direction to the subject line, your target audience will get confused and far less likely to open your email.

There is, of course, also the option of forgoing the preheader in which case, some email clients will take the alt text of the first image in your email campaign and use it instead. If you go down that path, make sure you’ve crafted relevant, descriptive and clear alt text for every single image (not just the first one!) or you risk things getting weird. 

The Power Of A Good Email Subject Line

Email inboxes are overrun with hundreds if not thousands of daily emails. Hence, making a great first impression with a catchy, clear and inspiring subject line is more important than ever. It can make all the difference between people engaging with your emails or sending them straight to the bin – or worse, marking them as spam.

A great email subject line can have a powerful impact on your audience. From the words you choose and adding emojis (or not) to personalisation and funny puns, writing the best email subject lines is an art you need to master to achieve your email marketing objectives. Oh, and did I mention email subject lines are pretty much the biggest factor in whether or not people open your email?

There are five essential ingredients you need to make your email subject lines powerful – 

  • Curiosity. Is your subject line interesting enough to make recipients wonder what the rest of the email has to say?
  • Urgency. Why should recipients open your email right now? What’s the hurry?
  • A tempting offer. What awesome rewards can recipients expect to find when they open your email?
  • Relevance. Is your subject line giving recipients the impression you are speaking directly to them?
  • Novelty. Is your subject line hinting recipients will learn something new, surprising and unusual if they open your email?

You won’t be able to squeeze all of these things in an email subject line since the recommended length is only 50 characters nor should you try. After all, you need to keep things short and punchy.

However, if you manage to add one or two of these ingredients to your email subject lines, you will see a significant improvement in open and engagement rates.

Writing Email Subject Lines 101

Have you ever had that sinking feeling of spending an entire day crafting the most amazing email campaign thinking you nailed everything, especially the subject line, only to check your reporting and see disappointingly low open rates? 

Depressing, I know but there’s no need to overstress because once you master the art of writing email subject lines, you’ll never have to see gloomy results again.

Ready to find out how to nail writing email subject lines that convert like crazy?

Urgency

How many times have you seen the phrase “Act Now!” in infomercials and other digital marketing promo materials? As much as it inspires urgency and scarcity, I wouldn’t recommend using that exact language in your email subject lines. 

Yes, urgency in subject lines is important as it compels your audience to open and engage with your emails. But… it needs to be implemented creatively, strategically and sparingly. Otherwise, you might end up being known as “the brand that cried wolf”.

Remember, urgency inspires action. So, try to limit such email subject lines to when the situation truly calls for immediate action.

Email Subject Lines That Inspire URGENCY – 

  • Uh-Oh! Looks like your subscription is expiring…
  • SALE Will End Tonight!
  • Grab Your Coupon Before it Expires!
  • 60% OFF all products until THIS weekend

Curiosity

Humans are curious creatures. We don’t like leaving things unfinished or having gaps in our knowledge. So, leverage these feelings by leaving your email subject lines open-ended like cliffhangers in books. Trust me, your recipients will not be able to stop themselves from opening your email campaigns. But remember, your subject line must align with your brand and should not be too obscure or it’ll end up in the spam folder.

CURIOSITY Inducing Email Subject Lines – 

  • Don’t Open This Email!
  • Last Chance To See What This Email Is All About
  • 10 Bizzare Money Habits Making People Richer
  • Top Secrets of Email Marketing Influencers

Greed

Ultimately, people love shiny new stuff and thrilling new experiences – especially if it all comes free or, at least, at an extremely discounted rate. You might not perceive yourself as greedy but tell me honestly – would you pass up a great offer or a gift (even if you don’t need the product right now)? I didn’t think so.

Thus, why not mention your irresistible offer directly in the subject line? I’m much more engaged and willing to open emails when the subject lines hint at a sweet offer or “free stuff”.

GREEDY Email Subject Lines – 

  • 1 day only: 25% OFF on your next purchase
  • We can’t be wrong!  Open and we’ll prove it.
  • Great news: Product Prices Just DROPPED
  • Hi [FirstName], Have you claimed your free trial?

Personalisation

Did you know that personalised email subject lines boost open rates by 26%

Adding a recipient’s first name to your email subject line is a great way to personalise your email marketing. However, in this digital age, there are numerous ways to learn more about your target audience like their interests, preferences, likes and dislikes, occupation, age, location, etc. which you can later leverage when crafting your email subject lines, email copy and offers. Pretty much anything you can use to create a sense of familiarity and friendship, you should take advantage of and use.

PERSONALISED Email Subject Lines –

  • Happy Birthday [FirstName] – Surprise Inside!
  • Crazy Invitation [FirstName], I am Going to Buy You Lunch…
  • [FirstName], Thank you for being a loyal member!
  • Hey [FirstName], it’s BUY 1 GET 1 FREE week for your fav items!

Relevance 

Your target audience has tons of emails to filter through. So, make sure YOURS gets to the point quickly from the get-go – i.e. the subject line.

Think about this… most of the time, when people sign up to your email list they do so because they want to be kept informed or, at the very least, learn something beneficial. In either case, just craft email subject lines that include relevant, trending topics. By doing so, you will –

  • establish your business as an authority within your industry
  • improve open and engagement rates
  • compel recipients to share your awesomeness and knowledge with others

Remember, the best email subject lines make a promise and then deliver on that promise. Your email copy must deliver on the subject line promise too or you risk the complaint rate going through the roof.

Email Subject Lines That Incorporate RELEVANCE – 

  • Learn a New Skill in Just 15 Minutes Per Day
  • [FirstName], check out these top 5 time-saving tips
  • Psst, [FirstName]! Steal these email template ideas…
  • Hey [FirstName], I bet you don’t know this profit-boosting trick…

Email Subject Lines Best Practice

A successful email campaign starts with a great attention-grabbing subject line that is personalised, descriptive and gives your target audience a reason to open your email. But, how can you make sure YOU will achieve such email marketing success? 

Hint: implementing email subject lines best practice.

Keep it Sweet and Concise

On desktop, you can see 60 characters (sometimes even more) of an email’s subject line, while mobile devices will reveal 25 to 30 characters. You must ensure that your subject line is neither too short (one word) nor too long with such limited space. Otherwise, you risk changing the message in ways that are either distracting and confusing or embarrassing and, sometimes, even funny. 

According to email marketing gurus, the recommended subject line length is no more than 50 characters. If you are having trouble keeping your email subject lines short, sweet and on-point, you should carefully consider which words matter less and which matter more. For example, if you’re sending an order confirmation email which email subject line looks better – 

  • “Your order is being processed” 
  • Order #5687H42K3695N is being processed”

Hint: the one without number/letter gibberish.

Familiar ‘From’ Field

Who is the email coming from? Your company? Yourself? Your pet ferret?

When setting your ‘From’ field (a.k.a sender name/email address) make it as human as possible. Why? People are more inclined to open emails coming from an actual person rather than a brand. Yet, since they’ve signed up for your mailing list, your brand name popping in their inbox should be both expected and welcomed. 

If your sender name or email address is not recognisable or familiar to the recipient, it doesn’t matter what your subject line is because they’ll just ignore and delete it or, worse, mark it as spam. However, these ‘From’ field guidelines will help ensure neither happens – 

  • Newsletter – your company name
  • Sales emails – a sales rep or account manager’s name
  • Company updates/news – either the CMO or CEO (if known/recognised)

Avoid The “No-reply”

Considering the number of spam emails people receive daily, it comes as no surprise most hesitate to open emails from unfamiliar senders. Moreover, even fewer like talking to a robot.

Think about this… when you call a business and instead of reaching an actual person you have to listen to a long automated system, it’s frustrating. The same goes for “no-reply” emails.

Are you sending from a donotreply@yourdomain.com or no-reply@yourdomain.com address? Trust me when I say this, no one is looking forward to receiving emails from their ‘good friend’ Do Not Reply. 

Using such a sender email address is not only uninviting and less personable but also very unwelcoming and prevents people from adding you to their address book. Don’t be surprised if your open rates suffer if you opt for using such a sender address. In fact, 64% of recipients open an email based entirely on the sender’s name.

To avoid an accelerated drop in open rates, make sure to always send emails from an email address your subscribers are familiar with and to which they can reply if needed. If your email fails to allow the recipient to reply or ask questions, the possibility of them abandoning you and looking for a more personalised experience with a competitor will be very high.

Use Personalisation

Personalisation is key when writing email subject lines. Remember? I told you about it earlier.

Using a recipient’s first name or location (or any other relevant personal information) to personalise your email subject lines will add a sense of rapport and boost your open, engagement and click-through rates. 

As marketing extraordinaire Seth Godin says: People don’t want email. They want me-mail.”

In other words, getting a non-personalised email is about as exciting as receiving a “Dear Occupant” letter back in the snail mail era. 

A personalised touch here and there shows you know more about your recipients than just their email address. Just make sure you don’t go overboard with the personalisation or you might come across as a bit creepy and intrusive. 

If you can’t or don’t want to use personalisation in your email subject lines (which I highly recommend you DO!), substitute it with “you” or “yours” so it still sounds like you are addressing the recipient directly.

Segment Your Email List(s)

Your email database is the most valuable element of your email marketing strategy. Your subscribers’ interests, goals and needs differ. Thus, you can’t send all of them the same email.

What is email list segmentation? A targeting method used to divide an email list into smaller groups (segments) based on specific criteria. Usually, email segmentation is used as a personalisation approach to deliver more relevant and valuable email campaigns to your subscribers. Each segmented email list will help you cater to your subscribers’ independent needs/interests instead of crafting and sending one generic email campaign to all.

Email List Segmentation Best Practice >>>

Why is segmenting your email list(s) important? It helps you to craft highly targeted email subject lines (as well as campaigns) specific to your leads/subscribers/customers. Ah, it’s also proven that email list segmentation will boost your open and click-through rates and decrease unsubscribe rates.

Avoid False Promises

Your subject line makes a promise to your recipients. Thus, make sure you will make good on that commitment and DO NOT trick them into opening your email by making false promises

If you trick your audience, the possibility of them getting frustrated and never trusting your email subject lines will result in a significant drop in open rates and a notable increase in unsubscribe rates. Not to mention, you will risk having all future email campaigns being marked as spam and damaging your sender reputation. 

Reveal What’s Inside

Subscribers signed up to your mailing list for a reason and they have a clear idea of what to expect when they see your email popping into their inbox. 

For example, if someone opts-in for getting your latest ebook on “Email Personalisation and you are delivering it via email, it’s a magnificent idea to tell me what’s inside your email with a subject line like Your ebook awaits!”.

A subject line that makes it clear what you can expect to find or is waiting for you inside an email works much better than a simple mundane “Thank You!”, wouldn’t you agree?

Timing Is Everything

Sending the right email to the right person at the right time with the right subject line can make all the difference between recipients opening or deleting your email.

A perfect example for timing your email right is the classic reminder email with an “Uh-Oh, your subscription is about to expire” subject line sent at least a week (or two) before the recipient’s subscription expiry date. Or, a lifestyle business’s “The Best Wine Bars Close To Your Office” email on Friday just in time for drinks with colleagues and happy hour.

Best Time To Send Emails >>>

When determining the perfect timing for your email campaigns remember to be consistent. If your subscribers are used to seeing your emails in their inbox on Tuesday @ 11 a.m. with a cup of tea or Saturday @ 7 p.m. with a glass of wine, you don’t want to disappoint them – do you?

Make Your Audience Feel Special

The psychology of exclusivity is a powerful thing. 

When you make people feel special and part of a community, it creates a sense of belonging that inspires loyalty and compels people to open your emails.

Highly personalised email subject lines will make your recipients feel special precisely because of their tailored nature which, in turn, invokes a sense of consumer empowerment driving people towards the Holy Grail – a conversion. 

Think carefully about your subject line words/phrases. The right ones like “My Gift To You” or “Private Invite!” can do wonders to your email marketing metrics. But the wrong ones like “FREE TRIAL! Unlimited access. No $$$!” can lock your email in spam jail.

Ask A Compelling Question

Asking a question directly in your email subject line will draw the recipients’ attention. Especially, if the question is relevant to their needs/interests/preferences. For example, why not try email subject lines such as –

  • “What are our customers saying?”
  • “Is your website doing something wrong?”
  • “How to increase your profits?”
  • “Are you happy with your current email marketing software?”

The possibilities of posing a compelling question in your subject line are endless – as long as you know your audience well enough to target them the right way with the right content.

Be Punny & Funny

People love a good pun and they love to laugh. However, puns are a delicate art but… a pun that is good, or so bad that it’s good, will help you stand out in the cluttered subscribers’ inbox.

If you combine both in your email subject lines you will delight your target audience and spice up your email campaigns. 

Take a look at three brilliant punny email subject lines – 

  • JetBlue (airline) – “Land wander-ful low fares!”
  • Quirky (invention platform) – “Abra-cord-abra! Yep, we said it.”
  • Sephora (personal care & beauty products) – “We’re bringing sets-y back”

Have you ever read a subject line that tickled your funny bone but never opened the email? Using humour in email subject lines requires a pinch of creativity, a lot of thought and a cool sense of humour. 

Take a look at five funny email subject lines recipients won’t be able to resist – 

  • Open Table (REST-reservation service) – “Licking your phone never tasted so good!”
  • UncommonGoods (online retailer) “As You Wish” (a reference to The Princess Bride)
  • Thrillist (online media website) – ”Try To Avoid These 27 People On New Year’s Eve”
  • The Hustle (business & tech news) “Look what you did, you little jerk…” (Home Alone)
  • My personal favourite“3 bizarre steps to being better at your job”

DON’T USE CAPS or Overuse !!!

How would you feel if people START YELLING AT YOU? Frustrated? Annoyed?

If you don’t scream at people in real life neither should you in email. For instance, email subject lines like “OPEN NOW TO CLAIM YOUR FREE TRIAL” or “ACT NOW OR YOU’LL MISS OUT” are not going to get your emails opened. Instead, any emails with ALL CAPS subject lines will either be ignored or deleted or, worse, marked as spam.

How do you feel about exclamation marks (!)? Would you be interested in an email with a subject line like this – “60% OFF today only!!!!!!”?

Usually, the purpose of exclamation marks is not to convey excitement and get subscribers jumping up and down but rather to emphasise the exclusivity of a particular email. In fact, according to stats, 70% of businesses that use exclamation marks in their email subject lines witness a 10-20% increase in open rates. Therefore, exclamation marks do work and should be used as a part of a healthy email subject line strategy. Make sure you won’t overdo it though.

Ultimately, instead of using disruptive email subject line tactics like ALL CAPS and !!!!!!!, which rub people the wrong way, make sure your email subject lines will stand out in recipients’ inboxes by using personalisation, relevancy, catchy and funny language, and proper keywords.

Subject Line Keywords

There have been studies upon studies where marketers have tried to analyse the effectiveness of incorporating specific keywords in email subject lines. However, what works for some might not necessarily work for others. 

Therefore, the best way to determine YOUR perfect email subject line keywords is to try different ones, monitor your reporting to establish the winner(s) and then use said winner(s) when crafting your subject line AND email copy to increase open and engagement rates.

Let’s take a look at some of the top email subject line keywords (based on expert’s findings) – 

  • “upgrade”
  • “content” 
  • “promotional” 
  • “congratulations” 
  • “forecast” 
  • “voluntary” 
  • “monthly” 
  • “free”
  • “free delivery”  
  • “available” 
  • “thank you”
  • numbers (i.e. 55 ideas, 5-step guide) 
  • “order today”
  • “introducing” 
  • “celebrate” 
  • “buy” 
  • “latest” 
  • “special” 
  • “great deals”
  • “sale now”

Riddle me this… you have a reputable IP, near-perfect sender score, on-point subject line and both a physical address and unsubscribe link, why then is your email campaign still ending up in the spam folder? Hint: spam trigger words.

Most (if not all) email clients (i.e. Gmail, Yahoo!, Outlook, etc.) have spam filtering algorithms that are triggered when certain spam words either in the subject line or the email copy are detected. Hence, it’s crucial to know which specific words/phrases to avoid to prevent your emails from ending in the spam/junk folder.

Most common spam trigger words/phrases (per category) 

  • financial (business)credit card offers, no investment, no credit check, no hidden costs, a full refund, explode your business
  • general – chance, here, leave, amazing, cancel at any time, click here, congratulations, for only ($) (£), free, guaranteed, great offer
  • marketing click, click to remove, email harvest, increase sales, month trial offer, not spam, click below, direct email, removal instructions, increase traffic, mass email, opt-in, sale, this isn’t junk, we hate spam, visit our website
  • numbers 4U, billion dollars (or pounds), 50% off, join millions, one hundred percent guaranteed
  • offers financial freedom, important information regarding, no claim forms, no obligation, no gimmick, confidentiality on all orders, giving away, no catch
  • call-to-action get, print out and tax, give it away, see for yourself, sign up free today
  • free pretty much any phrase containing the word ‘free’
  • sense of urgency call free, do it today, apply online, don’t hesitate, great offer, order now, now only, offer expires, new customers only, get started now, call now, order today, special promotion, time-limited, urgent, take action now

Notice anything? For example, urgency being key when writing email subject lines and numbers being in the top keywords BUT both present in the commonly used spam trigger words list.

Test, Test, Test

All the tips, tricks and best practice I gave you are a great place to start. However, one important thing bears repeating – what works for some brands might not work as well for others. No need to panic though, that’s where A/B testing (a.k.a split testing) comes into play.

Think about this: Two roads diverged in a wood and you… let’s face it, you didn’t take the path less travelled. Instead, you pondered for waaay too long over which one would get you there faster and with fewer hiccups. Then, you spent the whole journey agonising over whether you’d made the right choice. 

You face the exact same dilemma when crafting email subject lines. You start thinking “should I run with this subject line or that one?” and, of course, the second you’ve committed to one and unleashed your email campaign on your target audience, you start obsessively refreshing your reporting worrying that the other subject line would have gotten a better response. 

The solution. As tempting as it may be to use your intuition to predict which subject line will make people open your emails, it is not a viable subject line strategy. To figure which version of your subject line (A or B) would perform better, without committing to either, you need A/B testing. A small portion of your email list will receive the two set up versions – half will see Version A and half will see Version B. Afterwards, your email marketing software will swiftly track the performance of both emails and “tell” you which version saw the most success. 

The more you test your email subject lines, the more you’ll come to know about your subscribers/customers and their interest/preferences.

Email Subject Lines Stats

If I haven’t already convinced you how crucial email subject lines are for the success of your email marketing, maybe these statistics will finally drive the point home – 

  • personalised email subject lines get a 26% boost in open rates
  • 82% of marketers send emails with no more than 60 characters in the subject line
  • words like “free”, “per cent off”, “help” and “reminder” in subject lines negatively impact open rates
  • adding the recipient’s first name to a subject line boosts open rates by over 18%
  • email subject lines with interactive content get 70% higher conversion rates
  • 45% of subscribers state they are likely to read an email because of who it’s from

Final Thoughts

It often takes us milliseconds to glance at a subject line and decide whether or not to open or ignore or delete an email. To ensure your email subject lines will be perfect and compel your target audience to take action they have to – 

  • provide value instead of misleading the recipient
  • be short, sweet and to-the-point – the recommended length for a subject line is no more than 50 characters
  • be focused on the topic and avoid any fluff or filler words
  • sound professional
  • be personalised
  • avoid YELLING at the recipient. 

Don’t forget that email subject lines are a vital element of the email headers which is the first thing spam email filters look at before popping your epic email into your recipient’s inbox. Therefore, be careful with –

  • ALL CAPS
  • overuse of exclamation (!) and question (?) marks
  • spam trigger words
  • lack of personalisation
  • overuse of words such as FREE, sale, special offer and the like

Ready to write the best email subject lines that will get your emails the attention they deserve?

Highly recommended further reading – 

1) Writing Marketing Emails 101
2) 27 Awesome Subject Line Ideas
3) Common Email Subject Line Mistakes
4) Email Marketing Campaign Checklist (PDF version here)

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