Writing an email subject line is a fine art that requires a high level of creativity as well as careful analysis of what customers respond to.

It’s not easy coming up with varied topics that pique the reader’s interest while avoid becoming monotonous or relying too heavily on sales and promotions.

Luckily there are a huge number of case studies published online that help to give marketers inspiration by revealing the type of content and tactics that will increase engagement. But that doesn't mean that the subject line can be neglected in favour of focusing on the email content.

Responsys director of strategic services EMEA Jon Stanesby said that the subject line is crucially important, so shouldn't be seen as something that can be altered at the last minute.

If anything, the subject line should come first and then other elements should follow. More people see the subject line than any other element of the email campaign, so it’s absolutely vital to impress here.

But to make things easier, I’ve trawled the internet and come up with 10 things that should be avoided to ensure you don’t inadvertently harm your KPIs.

Obviously none of these rules are written in stone and it’s really up to marketers to test their own campaigns to find out what does and doesn’t work for their own customers, however this list does at least identify a few criteria to begin testing.

And for more information on this topic, check out our blog post detailing six case studies and an infographic on how to write effective email subject lines.

But, here are the 10 things that should be avoided...


In a recent Econsultancy survey 94% of businesses stated that personalisation is critical to their current and future success.

However too much personalisation in email, such as using the recipient's name in the subject line, can have a detrimental effect according to Stanesby.

Brands should also be wary of being too personal in subject lines because this can seem overly familiar. Personalising subject lines too frequently also diminishes the effect and is best avoided.

Overt requests for donations

Heartwarming research by MailChimp found that subject lines that make a request for charitable donations have a negative impact on open rates.

However choosing the correct wording can at least mitigate the apparently repellent effect of asking people to send money for a worthy cause.

The word ‘donate’ was found to have the most negative impact, while ‘helping’ and ‘fundraising’ were the least damaging. However the latter two words can of course be used in a wider variety of contexts.

'Last Chance'

In the aforementioned MailChimp study the phrase ‘Last Chance’ was found to have a hugely negative impact on open rates.

Obviously people don’t like to be reminded that they’re missing out on something they’ve already been emailed about.


Nothing says spam quite like a shouty, capped up subject line. It makes it difficult to read and is unlikely to have the desired effect of grabbing the reader’s attention.

As you can see in this example from my own spam folder, nothing says “I’m dodgy” quite like a capped up subject line offering a ‘LEGIT LOAN @ 3%’.

Sadly it seems that Gmail also feels that Apple and Advertising Week Europe are worthy of the spam bin...

The words 'confirm', 'join' or 'assistance'

A study by Baydin identified seven words that were unlikely to provoke a response from recipients. They were confirm, join, assistance, speaker, press, social, and invite.

Vague or uninteresting subjects

A case study by communications blog AWeber found that clarity is an important factor for boosting open rates.

It compared clear, concise subject lines versus more creative versions in a test that ran across 20 subject lines and was sent to more than 45,000 subscribers.

The results are not that surprising as the creative examples were often vague or uninteresting, so did little to grab the reader’s attention.

Across each channel the clear, descriptive subject lines far outperformed the creative versions:

Too many characters

Stanesby said that though the rules change between different industries, generally firms should avoid long subject lines.

20 to 30 characters is plenty because consumers won’t read past that and most of the wording will likely be cut off on the screen, particularly on mobile devices.

Indeed the effect is magnified on smartphones due to the small screen size, and with upwards of 40% of emails now being opened on mobile devices it’s an issue that marketers can’t ignore.

It’s not possible to narrow it down to a specific length as there are other factors that play a bigger role in driving high open rates, however data from Mailer Mailer indicates that the sweet spot is somewhere between four and 15 characters.

Exclamation marks!!!

It seems logical that including several exclamation marks in a subject line is going to put the recipient off as it has the look of spam.

However as yet I’ve failed to come across any research that proves this to be the case.

In fact a cursory glance at my inbox shows that brands are more than happy to use exclamation marks, as well as caps and the word ‘free’, which is often cited as a blacklisted term that is sure to trigger spam filters.

Even so, I’m going to stick my neck out and say that using more than one exclamation mark looks spammy and should be avoided.


A study by Adestra found that consumers are too smart to be fooled when marketers add in ‘FW:’ or ‘RE:’ to the subject line to give the appearance of familiarity.

In fact the respective click rates were 47.5% and 42.6% lower than average. So don’t try to outsmart your customers as it’s underhand and they’ll likely see through it.

Bad content marketing, or marketing bad content

The same previously mentioned Adestra study found that certain forms of content marketing can actually harm open rates.

For example, using the word ‘report’ saw opens drop by 23.7% while CTR fell by 54.8%. The same is true for ‘webinar’ with the stats dropping by 16.6% and 70.7% respectively.

Conversely if the content is good, people will consume it. So 'news' (+34.8%, +47.7%), 'bulletin' (+15.8%, +12.7%) and 'video' (+18.5%, +64.8%) work well.

David Moth

Published 19 November, 2013 by David Moth

David Moth is Editor and Head of Social at Econsultancy. You can follow him on Twitter or connect via LinkedIn

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Comments (16)

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Jordie van Rijn

Jordie van Rijn, email marketing specialist at emailmonday

Hi David,
Tthis must be a 'trick' to get email marketers to respond, so that works! : ). But one thing I would do is not to contradict myself in subjectline versus email.

Like the title of this post "10 things to avoid using in your email subject lines", but then after the first quote: "...to make things easier, I’ve trawled the internet and come up with NINE things that should ....."

There has been a lot of debate on subjectline length, but i can say that the picture MailerMailer is painting misses some refinement and a huge part of the scale.

The report by Adestra is much more detailed in the subj length too:

over 4 years ago



Great article.. those tricks are amazing.. next time i will keep these on my mind.. really fun read

over 4 years ago


George Liapis, eMarketing at Buldoza S.A.

Very nice article David and kudos to Jordie - I was about to quote Adestra's report (cause we 've seen similar results in our case) but he already did

over 4 years ago

Jamie Wonnacott

Jamie Wonnacott, New Vision Media

We're just starting out in the realms of email campaigns so thanks for gathering these thoughts - they'll be considered again for Friday's Newsletter!

over 4 years ago



Amused but not surprised at the 'heartwarming research'

Interesting that video had a respectable CTR, which seems to buck the trend. Common sense is often forgotten so this is a helpful article which I'll bookmark - thank you

over 4 years ago


Alex C, Manager at Croucher Edwards

Thanks David. Some very salient points here.

I'd be interested to see the click rates for those emails with a subject line of between 4 and 15 characters. From past experience I've learned that short (and often ambiguous) subject lines tend to boast reasonably good open rates, yet perform terribly in terms of engagement and CTR.

However, I suppose this approach allows rogue agencies to skew the data in their favour in the event of a poorly performing campaign. "Well the email generated a 64% open rate which is awesome, so it must be your product that sucks!"

over 4 years ago



Nice article, it is still useful to remind us rules like these. However I wonder about the "webinar" word: how would you replace it in your subject line?

over 4 years ago


jeremy swinfen green

Good stuff but I am not sure about the "don't personaalise" tip: I have seen a fair amount of evidence that indicates using a name is effective. For example: http://blog.eloqua.com/personalize-email/. But as always I suppose it depends on the audience and the product.

over 4 years ago


Tess Marshall

Thanks for pulling all these resources together - really useful.

I'm definitely on the anti side when it comes to personalising subject lines. Reminds me of salesmen over-using your name in conversation. And when the email's in my in-box, I already know it's addressed to me!

over 4 years ago


Darren Hepburn

Great shout Jordie, I've seen Perry Malm from Adestra present a seminar on subject lines, he knows his stuff!


over 4 years ago

David Moth

David Moth, Managing Editor at Barclaycard

Thanks for your comments everyone.

@Jordie, it wasn't intended to provoke a reaction at all! The idea was to give people some ideas for how to optimise subject lines and flag up some interesting surveys. And thanks for pointing out my numbering error, I added one final point in at the last minute and forgot to change that nine to 10.

over 4 years ago



In working with thousands of subscribers on a daily basis, I've learned one fact that trumps all others: Know Your Audience. Don't talk down to them, don't over-simplify, and don't give them more than they need to know in the sub line. You want to draw them in, make them want to open the email to learn more. Give them the basics in the sub line, but leave them wondering what it's all about so they open it to get specifics.

I agree with avoiding the use of all caps, exclamation points and the "re:" or "fwd:" in the sub line - but here's another big issue for spam filters - the word "free" - whether in all caps or not. Using it in your sub line or in the body of the email will cause it to hit spam filters more often than not. (You may occasionally get away with it, but it depends on the recipient's email service and what it considers spammy.)

over 4 years ago

Parry Malm

Parry Malm, CEO at Phrasee Ltd.

Hi everyone, thanks for the shoutouts to my research (and cheers Darren, although I'm not sure who this pErry guy is!)

So, the thing about subject line length is that there is no durable correlation in the long term. However, there is substantial short term variance on a campaign-to-campaign basis. This is because email is strongly trending towards usability. What do I mean?

If you've got something quick to say, i.e. "Buy this now" etc., then don't waste subject line characters. For hard sell messages, short, direct and punchy subject lines work better.

But for more content-focused lines, for example for newsletters etc, longer subject lines tend to perform better. Why? Because your subject line is basically snippet content that is a psychological cue to read on.

Anyways. I've spent more time looking at subject lines than is healthy, and as a result my mom is super proud. The point is, if you aren't testing out these things, then you're treading water, which is much less fun than chucking yourself down a waterslide.

If anyone wants to see my research follow the Econsultancy link above posted by Darren. It will change your life (it won't, but it's an interesting set of statistics.)

over 4 years ago



I'm not so sure about 'last chance': since it's typically the sort of email that comes after a series of sollicitations, it sounds to me as though the lower open rates may be caused by the fact that those who may be interested have already clicked, rather than by the subject line itself.

over 4 years ago


Dan Williamson

Can I also add 'Name dropping a brand, then not including it in the body of the email'?

Just got an email from idio Ltd which had the following subject line: 'Learn how Red Bull avoids content marketing blindness'

The brand is then not mentioned or alluded to in any of the four articles the email is then promoting.

Naturally, users are going to close it down and move on rather than try to click each article hoping to see something about Red Bull...

over 4 years ago

David Moth

David Moth, Managing Editor at Barclaycard

@Dan, I've had a few of those in the past from Seetickets offering gig tickets for bands that weren't mentioned in the actual email.

over 4 years ago

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