Did You Know This About Email Subject Lines?

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email subject lines

Email messages are important — but sending an email message with a great subject line is even more important. It’s important for one to one communication or for email newsletters.

SendGrid analyzed 18 million emails and distilled three important aspects of what makes a great email subject line.

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Shorten Subject Headers

While seven words is the most common subject line word length (14.0 percent of subject lines), three word subject lines (1.6 percent of subject lines) have the highest engagement rates (21.2 percent, compared to 17.2 percent overall and 15.8 percent for seven word subject lines).

Measuring engagement rates by number of character lines tells a similar story: longer subject lines have lower engagement rates.

Past 15 characters, each extra character is correlated with a 0.03 percent absolute decrease in engagement rate (or about one percent per 33 characters).

Carefully Chosen Buzzwords

Recipients prefer certain words over others.  Subject lines referring to yesterday and tomorrow” have higher engagement rates (20.5 percent and 22.3 percent, respectively)  than “today” (11.8 percent).

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Subject lines with soon have higher engagement rates (21.9 percent) versus subject lines referring to now.”

Email subject lines that use the word free have significantly lower engagement rates (13.1 percent versus 17.2 percent for “free” – free subject lines).

No Links and Hashtags

Subject lines that contain URLs do poorly, with average engagement rates of 9.9 percent (compared to 17.2 percent for subject lines that do not contain a URL). Subject lines with URLs in them are rare (fewer than 0.4 percent of emails).

Subject lines that contain #hashtags do poorly, with average engagement rates of 10.5 percent for subject lines with a single hashtag (compared to 17.2 percent for subject lines that do not contain a #hashtag). Thankfully, emails with hashtags in them are rare (fewer than 0.2 percent of emails).

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3 Reactions
  1. Nice article – I had no idea re length of email subject lines (although I guessed about using the word ‘free’ – it puts me off!)

    Thanks for this – will remember this when writing my next email campaign.

  2. I am glad you shared such post which gave us a lot of informative key points to email subject lines.I love the fact that subject lines are so impactful that it literally cause the receiver to open the emails, which is very advantageous to every business out there who is doing email marketing.Our business uses a tool called Easysendy Pro for hybrid email marketing service, and I really liked the way it gives us good conversions and so many options for those attractive templates.