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The Dos and Don’ts of Email Subject Lines

When it comes to increasing the open rate of your emails, there is one area that is often forgotten about: the subject line. Your audience’s time is valuable, don’t assume they want to read what you’ve written. The subject line is often the first impression you will make and can therefore make a huge impact on whether your email campaign is successful or not.

“Research shows that short subject lines get the highest performance. How short? Data suggests that under 15 characters maximizes your open rate while 28-39 characters maximizes your click rate. Some industry thought leaders, such as hubspot and MailChimp, recommend restricting your subject lines to 50 characters max.”

So what makes a great subject line and how can you use this within your own campaigns? Here are a few of dos and don’ts you definitely want to read.


  1. Make sure it’s clear who your email is from. You don’t want your recipients to be confused when your email shows up in their inbox.
  1. Use questions. A recent study by Mailchimp found that subject lines phrased as questions performed better than similar subject lines that were phrased as statements.
  1. Keep it short. We’ve already stated that people are short of time and you’ve got to respect this. The same study by Mailchimp found that longer subject lines performed worse than shorter ones. Keep it under 50 characters. Short subject lines, specifically with fifteen characters or fewer, have the highest open rates.
  1. Be specific. It should be obvious what your message is. Leaving your recipients guessing can cause frustration and lead them to ignore or delete your email.

“When it comes to email marketing, the best subject lines tell what’s inside, and the worst subject lines sell what’s inside.”

– Mailchimp

5. Include a call to action. Sometimes, it’s helpful to clearly inform readers what their next step should be. Otherwise, their eyes will just skim right over your subject line without understanding that an action is required on their part.

Do Not:

  1. Avoid overused and spammy words such as “free sample, new customer only, take action now.” They will mostly likely decrease click rate and might even trigger spam filters. Make sure you read HubSpot’s Ultimate List of Email Spam Trigger Words.
  1. Use all capital letters. There’s really no need to shout your message at your email recipients. Trust us, they get it.
  2. Include first names or personalization in subject lines. In a study conducted by MailerMailer last year, click-through rates and open rates were both negatively impacted by personalized subject lines.
  1. Send out emails asking for help. Fear of being scammed has made many consumers wary of emails that always ask for help or assistance.
  2. Include numbers. While numbers can often increase engagement levels and pique interest, they also put your email in danger of getting lost in the abundance of “special offers” floating around in cyberspace.

In conclusion, your email subject lines need to be optimized if you are looking to get the best results from your email marketing campaigns. Many of the best practices are easy to implement and don’t cost money. Remember to carefully choose your subject line to succeed.

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