Email Subject Line Types & Best Practices For Higher Open Rates

17 Aug 2023

The very first thing someone will see when your email campaign lands in their inbox is the subject line.

So let’s make it count!

It’s not always easy to nail subject lines. Get it wrong, and you could bore or even confuse your subscribers. This could lead them to deleting or unsubscribing without even reading your message. 

Understanding the different types of email subject lines is key, since like a box of crayons, every type is going to offer something different.

As the world’s first sustainable email marketing platform, here are the top subject line types to know so you can try them for your next campaign. 

Before We Start - Check Out The EcoSend AI Subject Line Generator 

Nothing like starting a post with a free tool to share! 

If you find yourself struggling to come up with exciting subject lines, our AI Subject Line Generator could help with that writer’s block.

It’s completely free to use, and only takes a few seconds to generate endless subject lines for you to choose from.

Like what you see? We’d appreciate it if you’d share it with your friends! 

🤖 ✍️ - Take me to the EcoSend AI Subject Line Generator 


Picture any thought leaders you watch on YouTube or listen to on a podcast. They grab your attention right?

With an authority-driven subject line, the aim is to do the same but within the few words available in a subject line.

Authority is about confidence and empowerment. What we want users to think is that by opening the email they will gain invaluable knowledge on how to do something they are interested in. 


‘How I earned $1,000 a day from my side hustles’

‘What it’s really like to be a CEO at 18’

‘Why you’re not making progress at the gym and how to fix it’


If social media has taught us anything, it’s that humans like to compare themselves to other people. Beyond looks, we’re also talking skills, success and general life progress.

Comparison emails tap into the urge we all have to be satisfied by progress reports or stats, showing us where we are now compared to where we were, or even where we’d like to eventually be.

When comparison emails consider relevance for the user, they generate intrigue making it more likely for someone to not only open the email but also generate clicks. 


‘See how house prices in your street compare with your city’

‘How do your workouts match up with our gym members?’

‘The top 10 skills all marketers need to improve - do you relate?’


Back when everyone still worked in an office, when someone would walk in with unmissable news about what happened over the weekend, it’s fair to say that person would get everyone’s attention.

Curiosity isn’t always perceived as ‘gossip’. Though, it does involve really wanting to know about something, or even how something can be done easier. 

So when writing a subject line based on curiosity, the aim is to give a teaser within a couple of words that piques interest just enough to make someone click onto the message.

It’s almost as if their day will be lacking if they don’t because they will miss out on a vital piece of information or a pro tip. 


‘One hack everyone needs in their morning routine’

‘You won’t believe the new trend sweeping Hollywood’

‘The research that proves what your grandma told you was true’


The power that comes from holding a certain credit card, or even having special access in a building can be replicated in the form of an exclusivity email.

In reality, if a company has 100,000 subscribers, being part of the mailing list might not actually be that exclusive. However, by carefully wording the subject line it can be made to seem that way and generate more sales in the process! 

Exclusivity is all about making that subscriber feel like they are your only customer through highly personalised communication which showers them in adoration. 


‘Our subscriber only 50% off event and you’re invited’

‘Exclusive offer for members only inside’

‘Your reward points summary + free gift for subscribing’


Everyone appreciates being spoken to on a personal level, whether that’s by name, or by mentioning specific interests or details relevant to that user.

Personal emails usually contain specific information in the subject line, most commonly the person’s first name. 

By seeing their name in their inbox, it sounds as if you’re speaking directly to them, rather than just sending a mass email campaign to everyone.

P.S: With email marketing automation, the campaigns can actually be mass sent, yet will appear highly personalised giving marketers the best of both worlds!  


‘[name], the [product name] you’ve been browsing is on sale!’

‘Happy birthday, [name]! Your treat is inside’

‘As a new customer, don’t miss out on these perks [name]


When crafting your subject line as a reminder, there’s a couple of things that can be achieved.

The first is a gentle prompt to encourage users to complete a certain action, such as make a payment, book a service or update their details. 

Also, reminder emails can be used to promote customer engagement, to avoid any surprises such as missing out on a product, or to know when a payment is due to be taken from their account.

So whenever wanting to prompt users, a reminder in the subject line can bring focus to encourage the task to be completed. 


‘[name], your next dentist visit is due’

‘Don’t forget to activate your account’

‘Your subscription is due for auto-renewal’


As the same suggests, urgency is when something just can’t wait - at least that’s how the subject line will phrase it anyway.

Often, urgency style emails will contain emojis, with ‘🚨’ being the classic one. ALL CAPS is another way to stop people in their tracks.

Something to note with urgency emails is that they should be used sparingly. It’s a major mistake to make every email urgent as this actually drives user fatigue, and is more likely to result in a move to the spam box or a hit of the unsubscribe button.

But for those rare occasions which have genuine merit, you can definitely get away with creating a bit of noise. 


‘Hurry, 70% off all products for today only!’

‘Last chance to shop our biggest ever sale’

‘Use your reward points before they expire, [name]’

Email Subject Line Best Practices 

Now you know what the main types of email subject lines are, it would be definitely useful to know how to put them to best use.

Our unmissable free tips include:

DO - Experiment with subject line types rather than relying on the same formats. 

DO - Pay attention to email analytics to see which subject line types have higher open and click-through rates

DO - Keep subject lines as short as possible

DO - A/B testing to perfect your subject lines and email content

DO - Include a hook or CTA in your subject lines to grab attention or drive a specific action

Don’t - Use excessive punctuation in subject lines

Don’t - Use excessive emojis in subject lines

Don’t - Include spam trigger words which could get your domain blacklisted 

Don’t - Be too vague about what the email is about within the subject line 

Don’t - Overdo a sense of urgency in every campaign 

EcoSend - Start Your Free Trial Of Our Email Marketing Platform Today 

Every professional email marketer requires an email marketing platform to store user data, create campaigns and then send those campaigns.

EcoSend is the world’s first sustainable email marketing platform. Our tool is packed full of features, yet runs on renewable energy sources making your email sending far better for the planet.

Our plans start at just $49 per month, and you can sign up for your free trial right here

Want to know more about us? Check out the EcoSend Podcast or give our blog a read.  

You can also drop us a message to ask us anything about EcoSend or schedule a free demo by heading to our contact page (will open up in a new tab). 

About the author

Rachael O'Flaherty

Content Writer

Email marketing without the carbon footprint

The climate conscious email marketing platform. Send your first campaign today.

  • Free Email Templates

  • Smart Segmentation

  • Lead Forms

  • Automated Campaigns

  • Automatic Offsetting

  • Team Sharing

  • HTML Email Editor

  • Multi-channel Campaigns

  • Drip Campaigns

  • MailChimp Import

  • Zapier Integration

  • Powerful API

Email marketing without the carbon footprint

The climate conscious email marketing platform. Send your first campaign today.

  • Free Email Templates

  • Smart Segmentation

  • Lead Forms

  • Automated Campaigns

  • Automatic Offsetting

  • Team Sharing

  • HTML Email Editor

  • Multi-channel Campaigns

  • Drip Campaigns

  • MailChimp Import

  • Zapier Integration

  • Powerful API