Optimize the subject line of an email

Best practices for writing a subject line that ensures email deliverability and opens

Your subject line is one of the most important parts of your marketing strategy. It’s the first thing your contacts see and is usually what makes them decide to open — or not open — your email, if it even makes it to the inbox!

No matter how well-crafted your email is or how valuable the content is, you miss out on a lot of engagement, and in turn potential revenue or conversion, if your contacts don’t open it. When used correctly, the subject line can help your email avoid the junk mail folder and improve your open rates.

• Characteristics of an effective subject line
• Examples of good subject lines
• What works for your readers 

Characteristics of an effective subject line 

Short and descriptive

Readers scan their inboxes in a split second, so it’s important to keep your subject line short and sweet. Additionally, most email providers cut off subject lines that are greater than 60 characters, and more and more users are opening their emails on mobile devices. To ensure your message comes across, your subject line should have no more than 4-7 words or 40 characters.
 

Did you know? Sometimes subject lines that are only one or two words can really stand out in the inbox and get the most engagement!

Entice the reader to open

A subject line should pique your readers' interest, act as a teaser, or state a benefit of opening the email. If you're including an offer, make sure the subject line and email body doesn't contain spam-like characteristics. Adding personalized contact details to your subject line, such as your contact's first name, help catch your recipients' attention and make them feel valued. Emoji are another great way to stand out in the inbox and convey a certain feeling or emotion related to your email content — but we recommend using just one.
 

Tip: Take advantage of the email preheader in conjunction with your subject line to help get your point across in the inbox, while keeping your subject line short. It also lets you get a little more creative!

Avoid spam-like characteristics

Spammers use a variety of tactics that you'll want to avoid in your emails to improve your open rate and to avoid triggering spam filters:

• Words like "free," "guarantee," "spam," "viagra," "sex," etc.
• Phrases like "be amazed," "your income," "subject to credit approval," "earn XXX per week," "act now"
• Uppercase - WRITING IN ALL CAPS
• Punctuation - Excessive use of ..., !!! and ???
• Symbols - Excessive use of $$, %, and other symbols, like emoji. 

If your subject line doesn't comply with these guidelines, your email may be routed directly into your contacts' junk or spam folders.

Examples of good subject lines

The purpose of the subject line is to grab your readers' attention so they continue reading. You know your audience best — think about what made them join your contact list in the first place. Not sure how to go about crafting your subject line? Start with these questions:

• What’s your email about? - Your subject line should give an indication of what's inside the email so that your contacts don’t feel misled after opening.
• What’s the benefit of opening? - Your contacts want to know what's in it for them. Is there a coupon or sale inside? Valuable information or exciting news? Let your contacts know why they should open your email.
• What action do you want them to take once they open? - If you're asking your contacts to register for an event, volunteer, or simply check out your latest products, this is great information to include in your subject line or preheader.
• Is it personalized? - Personalized subject lines can result in more engagement because they help your recipients feel like you're talking directly to them, rather than sending a generic mass email. Even simply using the words “you” and “your” can help it feel more personalized.

Ask a question

Questions are a great way to stand out in the inbox and pique your readers' curiosity about what your email includes.

Share something of value

Are your readers looking for specific information or expertise from you? If you have something helpful to share, call it out in the subject line to let them know exactly what they're getting.

Create a sense of urgency

Did your readers sign up for coupons or sale information? Or are you offering something for a short period of time? Let your subject line create a sense of urgency that will encourage them to act now, instead of putting it off until later. If applicable, include a deadline. Just remember, avoid misleading your contacts with an excessive sense of urgency if it doesn’t exist.

And so much more

Just because you have to be mindful of spam filters, that doesn't mean you can't have some fun too! While you want to make sure the tone of your subject line fits with your brand, you can still get a little creative and spice things up with these ideas:

• Use alliteration, the concept of using multiple words that begin with the same letter.
  
  
   
• Try to rhyme.
  
  
   
• Incorporate recognizable quotes or sayings, such as from history or pop culture.
  
  
   
• Make them laugh with a pun or joke that relates to your email topic or call to action.
  
  
   
• Pull at their heartstrings.
  
  
   

What works for your readers

Now that you understand some of the basics and you've seen some examples in action, it's time for you to try out some subject lines with your own readers!

• Try out a new subject line for your next email. Be sure to always send a test version to ensure your email doesn't go into the spam or junk folder, and to see how your subject line looks in the inbox on a desktop and mobile. If possible, it's a good idea to send test emails to a few different email clients, such as Gmail, Outlook, and Yahoo, to check the deliverability and readability across the board.
• If you're not sure a subject line will resonate with your contacts, try A/B Testing two different subject lines to see which one your readers prefer. 
• Once sent, check your email reporting to track how different subject lines affect your open rates.

Learn more: Here are more tips for crafting an effective subject line and preheader pair that will inspire opens.

Questions?