Tis the season for evaluation, so I've looked back on Passle's weekly newsletter. A subject line is essentially a big shiny sign which, if successful, leads many people to open your email. It's an important metric in that it shows what moves our subscribers to open up an email rather than make another cup of coffee.

Open rates and subject lines

In terms of both open rate percentages and unique opens, these were our ten most popular subject lines:

• Brexit: it’s important to keep talking 
• #RIPTwitter? 
• No blog is an island 
• New year, new editorial calendar! 
• Why we need to stop focusing on vanity metrics
• 5 things to do after you hit 'publish'
• Don't put all your subject lines in one basket
• Are you cashing in on your company culture? 
• Lego, Trump, and Authentic B2B Communication 
• Be more octopus with your content! 

What conclusions to draw from these? 

• It's nice to see positive feedback for our stranger titles ('Be more octopus with your content!', 'Don't put all your subject lines in one basket'). 
• Topical subject lines are good performers, whether that's Brexit, Trump, or the then trending hashtag #RIPTwitter. Why not put your twist on the news in your next newsletter?
• Ask questions. Two out the top ten have a question mark, with a third beginning with a 'Why'. Questions are a great way of engaging your audience.

Clicks and subject lines

It's no good having a great open rate if no one then engages with your newsletter's content, whether that's a single call-to-action or multiple links. In our case, we distribute weekly the content created on blog.passle.net using Passle's newsletter tool so there are at least eight links in each newsletter for subscribers to click.

Here are the 10 email subject lines that converted into the most clicks for us:

• New year, new editorial calendar! 
• #RIPTwitter?
• Throw away that old mailing list no one cares about! 
• How do you create a winning Passle post?
• 5 things to do after you hit 'publish' 
• 11 common mistakes company blogs make 
• Lists, lists, everyone loves lists! 
• 21 content marketing strategies 
• Lego, Trump, and Authentic B2B Communication
• 5 tips to optimize your LinkedIn profile 

As you can see, three of these were also in the most opened emails ('#RIPTwitter?', '5 things to do after you hit 'publish'', 'Lego, Trump, and Authentic B2B Communication').

Note also the prevalence of list-type subject lines: '5 things to do after you hit 'publish'', '11 common mistakes company blogs make', '21 content marketing strategies', '5 tips to optimize your LinkedIn profile', and, arguably, 'Lists, lists, everyone loves lists!'.

My main conclusion from these subject lines is that: numbers convert because the content is clear. When you open an email titled '21 content marketing strategies', you do so ready to open some more content. This suggests that it's important to be upfront with your subject lines - less time is wasted on both sides that way.

Conclusion

If open rates matter the most to you, then be witty and topical in your subject lines. However, to attract prospects that will want to stay and hang around with you, then it's best to be upfront about your content. Mailchimp says that boring works best with subject lines, but every business is different, so the only thing you can do is keep testing to work out what is working for your audience.