Email marketing is still one of the most frequently used methods businesses use to stay in touch with customers, whether it's through e-newsletters, transactional messages or confirmations. While the sender of the message is the greatest determiner of whether the message will be opened, the subject line is the next biggest factor. Sixty-four percent of recipients open emails based on the organization that sent the message, while 47 percent open as a result of the subject line (1).

The email subject line tells readers what an email message is about, and it can make the difference between whether the email will be opened or not.

Length - Depending on the email client that customers are using, more of the subject line may be displayed. To avoid the message being cut off, keep it to 50 characters or fewer. The number of characters in the subject line predicts open rates as well. More than 60 percent of emails are now opened on mobile devices (2), which typically allow even fewer characters. This could be why subjects with between four and 15 characters had the highest open rates, and why those with more than 50 characters have the lowest percentage of open rates (3).

Personalization and Localization - When the information is more directly relevant to their interests, recipients are more likely to open the message. Setting the email client to personalize messages by the recipient's first name can increase open rates. Customers are also more likely to open messages that are targeted to their geographic region.

Avoid spammy language - Certain words and phrases, like "free" can get emails caught in spam filters if they are used too much throughout the email, including the subject line. In addition, some words can have a negative impact on open rates (4). Consider carefully before using these words:

  • Help
  • Percent off
  • Reminder

Content - Be as descriptive as possible. Open rates improve when the subject line accurately describes what the content of the message will be. When sending subsequent reminder emails, don't be too repetitive as open rates will continue to drop with each message sent.

A/B testing - Most email platforms provide metrics that allow marketers to determine how campaigns are performing. Each audience is different and will respond to unique messages. Testing can determine what works best for the specific market. Use metrics to test various types of subject lines and continue to improve performance and conversion rate over time.

1) Social Media Quickstarter

2) Marketing Land

3) Litmus Software

4) MailChimp

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