By Jim Sinor, Account Director, Epsilon International

Most commentators will tell you that the subject line of an e-mail is the only part which will be read by the recipient without actually opening the message. But the logical next step is to test, analyse and ultimately optimise this crucial element to improve the performance of e-mail marketing campaigns.

If the recipient doesn’t use a preview pane, the from and subject line are the only elements of your lovingly crafted message that will grab a readers attention and compel them to open the message. Therefore, the subject line has a huge impact on opening rates and campaign performance metrics.

Subject lines should be evocative and compelling, while clearly conveying the content and purpose of the e-mail. Analysis and optimisation of the subject line can lead to better open rates and ultimately higher conversion rates. Simply put, getting the subject line right means more revenue.

So what makes a good subject line?

It is considered best practice to include a unique offer in the main body of any marketing e-mail. Mentioning it in the subject line communicates the value of the message to the recipient and will encourage them to open it. Consumers like getting more than they bargained for.

Try and avoid using words or phrases commonly found in spam such as ‘save now’, ‘special offer’ and ‘free’. This will help ensure your marketing materials, bypass filters, land in inboxes and maximise the chances of catching the consumer’s attention.

It is very important to future deployments that your subject line is not seen as misleading. This could lead to a high opt-out rate among recipients and cause issues with ISPs who may prohibit future mailings.

Try and keep it short. There is still debate over the ideal length for subject lines, but it is acknowledged there is a correlation between low open rates and long subject lines. 55 characters is generally seen as the very top end of the scale, but analysis has shown that anything over 40 characters will see a drop in the open rate.

Turn off caps lock. Most filters will capture and bounce subject lines using excessive capital lettering, and even if this type of e-mail does land in an inbox, research has shown consumers react badly and quickly delete them.

Use numbers. Newspapers and magazines use numbers in headlines to boost sales and this also applies to subject lines. Consumers love lists, such as the ‘Top 10 Bars’ in their city, and this can be used to encourage e-mail recipients to open the message.

Try and personalise the subject line of an e-mail by using data unique to the recipient, the most common example being their name. This practice could backfire if the cleanliness of your customer data is not what it should be. But when done well, it creates an instant connection with the reader and makes a compelling reason to open the message.

Be prepared with fallback entries for fields without complete data. The terms ‘customer’ and ‘member’ are decent fallback entries and should seamlessly fill the gap.

This list is by no means exhaustive and every organisation is different, so none of the guidelines discussed here are set in stone. What works for a retailer won’t necessarily have the same effect for a not-for-profit charity.

How can you identify what works best for you?

Testing, testing and more testing. Testing various options on a segmented database simultaneously is traditionally thought to be the best way to optimise your subject lines. First segment your data; it’s important to do this randomly so that the only variables are the subject lines you’re going to test.

Then apply a subject line to each part of the data, with each subject line utilising a different factor in the tips outlined above. You then deploy, at the same time on the same day, and after 24 hours have a look at your open rates; this will give you an insight into what works best. Perform this exercise regularly, and always try and do things in the testing phase; this way you can keep your initial engagement fresh and your response metrics high.