How to write the perfect subject line for your email campaign

4 minute read

Perfect subject line

The subject line of your email is, believe it or not, one of the most important parts of your overall campaign – it’s the first thing the recipient sees when your email lands in their inbox. Sadly, it’s something that is far too often overlooked, and writing the perfect subject line can be tricky.

There are plenty of blog posts out there on how best to write subject lines for your email campaigns. In reality, every business, set of subscribers and email campaign is different, so your subject line needs to reflect this. The fact is, however, 69% of email recipients report email as spam based solely on its subject line, so getting it right is very important!

Different subject line styles

There are several styles of subject line that email marketing professionals like to use, and the debate between short, sharp subject lines against longer, more details subject lines has always been a battle ground. So let’s look at the positives and negatives for both camps…

Short subject lines


  • They can be used to leave the subscriber asking questions and wanting more; a past Barack Obama campaign is a perfect example here
  • Once in the inbox, email campaigns with shorter subject lines (6 to 10 words) do receive a higher open rate


  • Some people have reported that shorter subject lines (less than 50 character) are more likely to get consigned to the spam or junk folder
  • It can be hard to entice a subscriber to open and continue reading your campaign with such limited character space

Long subject lines


  • Longer subject lines allow you to include more details on what subscribers can expect once they’ve opened your email campaign
  • B2C businesses generally receive much better response with longer subject lines – over 80 characters seems to be a good number here
  • A 20 word subject line appears to be the real champion, with a 115% uplift in opens and 85% uplift in clicks


  • Statistics show that email campaigns with longer subject lines (over 50 characters) receive lower-than-average open rates

A/B testing different subject lines

One of the best ways to truly understand which subject lines work for your email campaigns is to start running subject line split tests. Using you can test up to five different campaigns simultaneously.

A/B testing

Having the ability to A/B test subject lines means you can create the same campaign multiple times, using different subject lines on each one. Ensuring each subject line is vastly different is likely to give you more interesting and actionable statistics. You can then send each campaign to an equal share of your subscriber database and analyse the performance of each campaign. Alternatively, you can send each campaign to a reduced number of subscribers, and then send the most popular campaign amongst those subscribers to your remaining database, automatically.

For full details on setting up an A/B test make sure you check out our knowledge base guide.