10 top tips for email subject lines

I’ve done few training sessions this week and one thing has been fairly consistent. Email subject lines. There’s a lot riding on a subject line as it’s the only opportunity you have to encourage someone to open your email, so you want it to be good.

“47% of recipients report choosing whether to open an email is based on the subject line alone.โ€

Wow! That’s a pretty big number. To avoid half your own audience missing out on your great email content, follow these guidelines for a tip top subject line.

1. Don’t make them too long

If your subject line has too many words, it’ll get truncated (cut off) when someone sees it in their email box which often doesn’t make sense, or, and this is way worse, can come across as embarrassingly different!

For example…

Deal of the day. Get high….
Add some sparkle to your wee…
Happy Hour from 7pm with free cock…


I’m sure you can work out what they mean’t to say but as you can see, long subject lines can get cut off and seriously lose their meaning so keep them short and sweet.

The optimum length is around 41 characters. Don’t start counting them – it’s much easier to count words, so use around 7 words and as I’ll talk about next, make the first 4 words the ones you really want your recipient to see.

2. The first 4 words of any subject line are the most important.

Depending on the device your recipient is using to view email, there may still be some truncation – even for a shorter subject line – and especially on mobile devices, so make sure that the first 4 words are the most important. 

A few good examples are;

‘10% off today only’
‘Our best kept secret is here’
‘The best budget friendly buys’

If you want a few more examples (it’s almost an endless supply!) then check out this comprehensive list from Optinmonster.

3. Optimise for engagement, not open rate

A study done by Marketo, proves how the length of an email subject line impacts not just open rate but overall engagement.

The table shows the different open rates resulting from a different number of words in the subject line. We can see that the top open rate results from the 4 word subject line (N.B. another reason why the first 4 words are so important),  

What’s really interesting is the ‘click to open’ rate. This is the actual clicks that result from an open (the theory here is that you can’t click in an email without opening it first). This metric is a real measure of engagement as the user has actually engaged enough to click a link. It’s this metric that gives the best result so this is why we optimise for 7 words rather than 4, BUT, the first 4 are still the most important so make sure you have your key words at the beginning.

To read about the full test, visit the Marketo website

4. Avoid unnecessary punctuation

We’ve all seen those emails with subject lines like ‘Buy today!’ or ‘You won’t want to miss this!’ A lot of punctuation is seen as spammy so be careful what you use.

‘Get 50% off your order now!!!!!!!!!!!’

Horrific isn’t it?

But I’ve seen emails with subject lines like this. Excessive use of the exclamation mark can seriously put people off opening your email and if they do, it’ll probably be to unsubscribe. I’m not saying don’t use them at all, in fact it can help incite a sense of urgency and a call to action when used sparingly – just not all the time.

Other punctuation marks and special characters like #@*, (yes, that’s a comma – avoid them) are known to trigger spam filters so you’ll want to avoid using them. Avoiding a comma can be tricky but use a hyphen instead.

Additionally using dodgy tactics like FW: or RE: in your subject line may get you a few extra opens but your recipients will only fall for that once – following that, it’s a surefire way to either end up in the spam filter or they’ll unsubscribe. 

5. Avoid too much capitalisation

Using too many capitals CAN LOOK LIKE SHOUTING! It’s not looked on favourably and your email might end up in the junk automatically.

Use proper capitalisation where appropriate – as you would in normal prose and you can’t go far wrong.

Having a capital at the beginning of each word is also okay, such as ’10 Top Tips For An Email Subject Line’.

6. Make it relevant and use preview text

Disjointed subjects lines and email content can encourage unsubscribes. If the recipient sees something like ‘Open now for 50% of everything!’ and then finds out that the email is actually all about a single new product, its likely to annoy your users. Make sure that what you put in the subject line is indicative of what the user will find when they open it.

Preview text can be useful here too. It isn’t always seen – most often, it’ll show on mobile devices – particularly android. It can be helpful in encouraging someone to open an email by providing supporting information to the subject line so make sure you use it if you can.

Here’s an example:

Subject line – ‘10% off today only’
Preview copy – ‘Discount available on all sale products’

7. Avoid using ‘spam’ words

The reason that some seemingly ordinary words and phrases trigger a spam filter is overuse. Too many emailers using words like ‘discount’ or ‘free’ have spoiled it for the rest of us.

I totally get that sometimes you just need to use the word ‘SALE’ but use it occasionally, not in every email. With overuse, not only will it lose it’s impact over time, but it’ll also start to trigger the spam filters.

These guys have a pretty comprehensive list of spam words to try an avoid so it’s worth a look.

8. Use personalisation occasionally

It does help to address someone by name as it conveys the impression that you know them. However, make sure you actually have the name data populated. It’s bad attention to detail having an email with a subject line that reads something like ‘Hi , we’ve got something special for you’ where there should be a name before the comma. But it’s worse to have ‘Hi <firstname>, we’ve got something special for you’ where the field isn’t even matched properly to what’s in the database.

Don’t overuse personalisation as it’ll begin to get too familiar to recipients and they’ll start to ignore it. Save it for something special like a birthday email or a really special sale or discount when it’ll have more impact and drive to open.

9. Be careful of emojis

These can look cool and in some cases, when used sparingly can have a positive effect on open rate. But be careful that they’ll actually work when someone views them. For instance, use them to enhance a subject line rather than use them to replace words.

๐Ÿ•Pizza delivery offer. Today only.
๐ŸŒžSummer Sale on now๐ŸŒž
Save ๐Ÿ’ท on our new baby gifts ๐Ÿ‘ถ
๐Ÿ•ถ๐Ÿ‘œ 20% off all accessories

Ask yourself, will the subject line still work if the emojis aren’t there? If the answer is no, then you need to rethink. The one above will all work without the emojis.

Be aware that some email clients will replace any emojis with quirky looking code which makes subject lines look really odd so make sure you test as much as you can and use them sparingly.

10. Test

Most email services provide an option for testing. Testing your subject lines first can give you a bit of a heads up – a trial run so to speak, before your carefully thought out email goes out to your entire list.

Most tests for subject lines work by sampling a percentage of the total number of recipients and splits it into equal groups for each subject line. Results will likely be automated and the ‘winning’ subject line will be rolled out to the rest of the recipients.

Keep it to 2 or 3 different variations and keep in mind that you might need to base success on clicks rather than opens (see point 3 above).

So there you have it. Who knew there was so much to say about a single line of copy! There’s a lot to be gained from a good subject line (and a lot to lose from a bad one!) so it’s worth spending the time on getting it right.

Let me know about any lines you’ve used, or any good (or bad) ones you may have seen, in the comments below.

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  1. This is exactly what I was struggling with this morning. There are some great tips here and links to help get those creative juices going. So focus on the first 4 words next time! Thanks Loren and new website looks fab

    1. Yes, Sarah. It’s amazing how much I can find to say about a subject line but hopefully, there’s some valuable tips here.

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