What could be more important in email marketing than subject lines? Without a good subject line your innovative content and beautiful design may as well not exist! So if you have time to spend on your emails, spend it on your subject line.

Supporting image

Of course boiling the content of your email down into a snappy one liner of 50 characters or less is not the easiest thing to do but consider their importance: Not only can subject lines cause your email to get caught in the spam filter, but even those who don’t end up opening will usually still read the subject line, making it the most visible part of your email.

All too Personal

A common trend in subject lines at the moment is personalisation. Stats fly around like “Personalization of email subject lines generated an increase of 8.8% in open rates over last year” (MailerMailer, 2013). I’m not suggesting these stats are fabricated but I am saying that taken out of context, some people may think that it’s a backstage pass to the 100% open rate concert.

It’s not that personalisation is bad, but it’s the ace in the whole and your secret weapon ready to bring out when it’s most needed. A great time to get personal with your subject lines is in a welcome email or special promotion. If you use it over and over again it loses all effect and has the disingenuous feel of mimicking a personal email.

What Trickery is This?

Supporting graphic

Breaking news: people aren’t stupid. Attempting to trick your audience with a misleading subject line is never a good idea. A common form of trickery I see used often by recruiters or job applicants is the old fake FW: or RE:. It only takes as much as opening the email to realise that it is neither a reply nor forwarded email. So you may have a higher open rate, but guess what – you can only hit unsubscribe or report as spam if you open the email!


In case you didn’t know already capitalisation is an incredibly bad idea in your email subject lines and preheader, along with using any special characters and exclamation marks.

You may really really want to urge people to open your email or shout about a special promotion, but capitalisation is never the answer. Not only does it make you look desperate, it can also trigger your email to get caught in the spam filter. Don’t even be tempted into capitalising one word like ‘FREE’. Initial capitalisation is the best format for your subject lines to take and looks the most professional, if you need to brush up on the rules there are plenty of writing and grammar tip sites such as Daily Writing Tips.

Words to Include

By this point you know not to get too personal and you know not to capitalise words so you’re probably thinking what can I put in my subject line. A report published by Adestra last year sampled subject lines from over 90,000 campaigns, so there’s no need to start testing from scratch.

Here are some of the best performing keywords in sampled subject lines:

Words that make people feel special

  • Exclusive
  • Limited
  • Special
  • Preview

Words that make people feel they’re getting a deal

  • Sale
  • % off
  • Save
  • Offer
  • Free delivery

Words that make people think they might miss out

  • Alert
  • Breaking
  • Latest
  • News
  • New
  • Don’t miss

I like to think of these as ‘power words’ that should be used wisely and honestly. If something’s not exclusive – don’t say it is and if something came out last year it is not the latest. Misusing these words will severely diminish their effect, and that’s a shame because used in the right way, they totally rule.

Don’t be Vague

Subject lines should be bold, punchy and stuffed full of great words and facts. Try to write subject lines in the style of bullet points rather than full sentences. Straightforward and descriptive is always best.

Ultimately you need to think how you can draw the most interesting stats, info, brands or deals out for your email’s content to create a subject line that your target audience won’t be able to resist. Weave your key points of interest with relevant words from this list for the best results.

Words to Avoid

Including the wrong words in your subject line will not only cause your open rates to drop and potentially damage your brand, but they could cause your emails to never see the light of day and get caught in the dreaded spam filter. Here are some of the worst words to put in your subject line:

  • Free
  • Buy
  • Success
  • Sex
  • Click
  • Guaranteed
  • Money making
  • Opportunity
  • Cash
  • Hidden

People love something free, but it’s a very risky word to include as it has been associated with so much spam in the past, so it is best to try and avoid using it in your subject line.

Mix It Up

As marketers we love consistency and we love brand. Unfortunately, if you keep a consistent approach to email marketing you will find what countless other email marketers have found before you: steadily declining open and click rates.

To keep your audience interested you have to keep things fresh! Of course this applies to your subject lines too. If you have a weekly newsletter you should not make your subject line “[My Company] Weekly Newsletter” every week. Instead try and draw what’s new that week into the subject line. Play around with the wording, the format (why not try using pipes or commas to get more content into your subject line?) and test test test!

By doing this you are constantly learning and improving your subject lines so that you can charm your audience with your email content and design.

Analyse subject line performance by single words and word combinations to see what your audience is responding to. If you find any words have a high impact on your open rates either negatively or positively then it is important to flag these so that you can draw on this research when crafting future subject lines.

Supporting image

Testing to this extent may seem technical and daunting, but you don’t need a lab just an inquiring mind and a bit of time.

Testing for Success

When you’re analysing that oh so sweet data, bear in mind that factors other than your subject line can affect your email’s open rate. Here are some other key elements that can have an impact on open rates:

  • Timing – this is a big one. You need to really consider when your audience is most likely to look at your email and have time to act on it
  • List quality – if you have an old stale email list then even the best, coolest, most exciting subject line can’t be expected to save your campaign

Follow more of my writings about email marketing and the like, or sign up to our guest list email and get great digital marketing blogs (and subject lines) delivered to your inbox.

Image credits

Similar Posts