24 Billion emails studied: discover the best subject line secrets


If you want someone, who doesn't know you personally, to open your email you need to choose your words wisely. Word selection for your emails start with the subject line of your email. The correct words in your subject line can increase the open rate for your emails or accelerate their deletion.


Find a tool to measure your email campaigns
Personalize your subject lines with first name and last name
Use time sensitive words such as urgent, but only if the content is time sensitive
The word freebie is better than free, but be careful with both as spam filters may stop these
People like new things so words such as announcement and invitation work better than reminder or cancellation
Avoid capitalization of all words and don’t overuse special characters
Subject lines of 4-15 words in length are optimal
The subject line must align with body content


First things first, you need a way to measure the open rates so that you can improve then. The open rate is simply the number of emails in your campaign which get opened by the people you sent to. Of course you want to maximize the open rate so that people will read what you have to say. A "read request" from your email software on your computer isn’t going to do the trick. You need a service! There are many services available with a variety of plans and Mailchimp provides a great email newsletter service with a zero cost basic account.

The findings in this article are based mainly from a recent study by Mailchimp, which looked at approximately 24 billion emails with a focus on the subject line of the emails as they relate to open rate.


Personalization refers to the use of the person’s name you are sending to. Both first and last names in the subject line provided a 33% increase in open rates. This was true for all industries investigated except the legal industry. The legal industry actually had a negative impact on open rates when names where used in the subject line.

Do you have first and last name for use in an email campaign? If you don't have first and last names perhaps you shouldn't be emailing these people as you need them to opt-in to your campaign or you could be breaking the law. New anti-spam legislation came into effect recently in Canada and in other parts of the world. You can find some more details about Canada’s anti-spam legislation here. Anti-spam legislation is important but will not be covered further in this article. You are urged to investigate anti-spam legislation further for your own country.

Specific words for specific reasons

If your email focuses on giving something away without a cost, using Freebie is 24% better than using Free. Overall Freebie did report a 26% positive impact on open rates. As many spam filters block emails which contain words like free and freebie, you want to use these words with caution and carefully measure your campaign results.

Adding words which imply time sensitivity did report to have a large positive effect on open rates. Urgent was the top word, which implied urgency, with almost 80% positive effect on open rates. Other words such as breaking, important and alert were reported to have a positive effect on open rates.

It is observed that people like new things and are indifferent to stuff they already know about. This observation was demonstrated with the use of announcement and invitation words which had a positive effect on open rates compared to reminder and cancellation words which had a negative effect on open rates. You would want to use words such as: Announcement, Announcing, Announced, invitation, and invites in your subject lines.

Unfortunately, most charity type words had a negative effect on open rates. You would want to avoid using words such as: Helping, Fundraising, Charity and Donate.

Capitalization and special characters

Although capitalization of the entire subject line did show a 7% positive impact on open rates, I would suggest not capitalizing everything as it may increase the chance of being caught up in spam filters and to some readers all capital letters is like screaming the text at them.

Using special characters such as: ! or * is okay but don’t use excessive special characters. Using multiple special characters in a row such as: !!! or *** is a sure sign to spam filters to stop the email. Limit the use of special characters if you have to use them.

Subject line length

From another study done by MailerMailer, they looked at over 60,000 campaigns to determine the optimum number of words to include in your subject line to positively affect open rates. Subject lines with 4-39 words accumulated the most open rates. The best of the best open rates were from subject lines with 4-15 words. So it would appear that the shorter the subject line the better.

Alignment of subject line with body content

Now that you have maximized your open rate by using carefully chosen subject line words you want your prospect to read your email and then do something. One really critical factor to keep people opening your emails is to make sure your subject line content matches your email body content.

If you entice someone to open your email with a cleaver subject line and the reader finds something out of alignment in your body copy or your body copy has nothing to do with the subject line, they will not read your email and most likely will never read any of your other emails sent in the future.

Subject line content should clearly indicate what the reader is going to see in the body of the email. Stay in alignment with the text in your subject line and your body copy and you have the chance of getting a repeat reader.

Of course the content of your email body has to benefit the reader in some way so that they feel their time was well spent. Remember that even the little time to open and read your email is like a little investment in your business by the reader. You want to replay that investment with something of value which is a great email with useful content.




Smile We can help your business with woman smiling and Wise Crescent Inc. logo

  • Recent
  • Popular
  • Tag