Beatriz Redondo Tejedor

// Head of Content

Learn how to write the perfect email subject line.

As in real life, first impressions matter in email marketing. Do you want to be the cool guy walking down the road everyone turns around to look at, or just that creep in slippers and a leopard-print bath robe most move away from when they cross paths in the street?

The inbox is a noisy and crowded place, and the fight for your contacts’ engagement is on. You have around 60 characters to capture your consumer’s attention in the subject line. How will you do it?


How to write the perfect email subject line

At Mailjet, we like talking about the secret weapons of email. That is, the key elements that can help you win the Battle of the Inbox. And leading the troop as Lord Commander is the subject line, a small but mighty sentence that can help you spike your contacts’ interest.



Following our recent blog post on what words you should avoid using in your subject line in order not to trigger spam alarms, we now want to show you how to create a perfect subject line for your business and increase your open rates.

There have been a ton of studies and debates posted on the web, arguing what phrases and power words produce higher open rates. Here, we’ll cherry pick the words, combinations and formatting of different subject lines, to help you write the best one to match your company’s brand voice and goals.


Email subject lines that don’t suck

Sounds like a good starting point, right? We’ll give you the key points on how to achieve this, but to see how these techniques look like in action, here are a few subject lines we’ve come across that have stood out in our inboxes.




Here we see the correct use of hexadecimal symbols. Lovebox has found a relevant symbol and combined with power words such as ‘First’ and ‘Announcement’ to get us to open the email.


This subject line tapped into our curiosity and FOMO (Fear of missing out) at the same. It made us think: “I’m invited? To where? Am I the only one invited? I feel special”. The invitation turned out to be a free beta invitation to a new music streaming service they are launching. The catchy subject line was not at all click-bait, the body of the email included an exclusive offer.  Let’s be honest… we did feel a bit special.

product hunt

We’ve been going on and on about emojis for quite some time now. Do they work? Which one’s best? We’d done a ton of research on the matter and have shared our findings with you. Maybe you’re not as excited to see them spread through the cyberspace as we are, but come on, they’re pretty cool. Here we see how Product Hunt uses them in a relevant context, creating a nostalgic feeling of mid-1990’s computer games.

pact coffee

We can always count on Pact Coffee to play on words with tongue and cheek. When it came to this email, you can see that they’re promoting a specific roast of coffee that they are running out of. The words “gone tomorrow” adds a certain urgency that makes us want to open and click. Again, some nice FOMO to trigger some engagement.


4 top tips to killer email subject lines

When it comes to constructing your subject line, there are three things you should always consider and follow like a ritual.

Length Matters in email subject lines

The verdict is still out on whether shorter subject lines drive more opens. A shorter subject line may be more likely to catch the reader’s attention, but it still has to be reflective of the content inside. As the subject line contains less detail on the content, the user might not find what’s inside the email interesting after having curiosity drive them to open it.

Additionally, you should be aware of each email client’s subject line preview length. For example, Gmail only shows the first 70 characters, where Hotmail / Live and Yahoo Mail show 60 and 46 characters respectively. Do some research on different mobile clients to find out the current limits too.

Tone and Voice

Positive or negative, questions or exclamations, vague sentences or more direct ones, FOMO, urgency… There are many ways in which we can communicate one same idea and playing around with different options might keep your emails fresh and enticing. However, your subject line (and your content) should always be aligned with your brand voice and tone. Having a recognizable style will go a long way.

Beta-i‘s newsletter does a great job at creating attractive subject lines that are unique to them, and is perfectly consistent with their brand voice. Have a look a some of their recent newsletters below.


P.S. Noticed how they use someone’s name as their From Name? This also contributed to their overall brand voice. Find more on From Names here.

Symbols and Emojis in email subject lines

Marketers have been using hexadecimal symbols for a while now, but they are not as widely used as you would expect because they are not compatible with all email clients. Same happens with emojis: not all email clients and devices work with these either. Whether you decide to opt for one or the other, they should always be used in context, otherwise it can have a bad effect on your brand and be seen as childish. 


Lastly, always A/B test. You can’t 100% know which subject line will work best, so set up an ‘A/X test’ to try out up to 10 different subject lines. For example, you might want to send your campaigns on Tuesday at noon with an A/B test in place and let it run for 20 hours, and then have the winning subject line and email be sent early on Wednesday morning so it’ll be one of the first in your recipients’ inbox when they get to work.

After A/B testing and sending a couple of campaigns, be sure you use ‘Campaign Comparison’ to see which campaigns worked best for your data-set and look to improve future ones! By comparing your results with your industry benchmarks you can always have specific goals to aim at and improve your email campaigns over time.


With all that said, now it’s time to get to work! Which of these techniques are you currently practicing and which ones are you looking to implement? Tell us on Twitter.


This blog post is an updated version of the post “How To Write The Perfect Subject Line“, published on the Mailjet blog on March 23rd, 2015 by Amir Jirbandey.