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[this subject line intentionally left blank]

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I love using Signals by Hubspot. It helps me see when people open my emails and how often they do so. And it’s free for up to 200 notifications per month. You can sign up here. (my referral link)

But that’s not what this blog post is about. I’d like to share some findings that the team at Signals recently unearthed from a deep probe of data collected from 6.4 million emails sent by Signals users.

Remarkably, they found that emails with no subject line—nothing at all, not even a word, left completely blank—were opened on average 8% more than those with a subject line.

Email Subject Line Graph

Any self-respecting email marketer knows the importance of great subject lines, so how can it be that ignoring this field completely actually improves open rates?

There are several reasons why an empty subject line may actually encourage more opens. Firstly, it’s actually quite rare to receive a zero subject line email, so the standout in your recipient’s inbox may be improved. In some email clients, having no subject may also place more focus on the opening lines of the email body copy, as in the example below:

Email with no subject line

For this to work, make sure your opening copy is compelling and on topic, otherwise your email may never get opened.

Another consideration is that new inbox layout formats currently being trialled like Gmail’s new tabbed inbox and card layout (where emails are shown on image-heavy cards much like Pinterest, rather than as a simple text list) may be easing us into an era where subject lines are less relevant than in the past. Which, of course, may also mean that the days of email clients gently reminding that we left our subject line empty may also be coming to an end:

Subject Line Empty Warning from Outlook

Few marketers I know currently dare to leave subject lines completely empty.Yet it turns out that this strategy might just work, every once in a while. It’s certainly worth throwing into a control A/B test. Give it a try and let me know what happens.