Hi [insert name] welcome to our awesomely helpful blog post! ☺

There’s an art to writing a good email subject line. If it’s a personal email to someone I know, they’ll be expecting something obscure, weird or occasionally offensive. 

However if you're sending a marketing email to a stranger, these are definitely things you’ll want to avoid.

The following is a revised and updated version of a previously published post, that takes into account new research published by our resident email marketing expert Parry Malm, as well as numerous expert sources, our own research and my own personal experience.

Sale now on!

Who cares? You're always having a sale, why pay attention this time?

Also according to MailChimp, free tends to trigger spam filters, as well as help, % off and reminder.

However the old adage that ‘sales messages trigger spam filters’ isn’t necessarily true anymore. 

Just describe the details of your sale in the most straightforward and concise manner possible, without relying on manipulation. 

If you’re a company that hasn’t been mixing up its marketing messages and instead bombarding your recipient's in-box with repetitive offers saying deals or sale ending soon, you're just going to get ignored.


As Parry Malm stated in his article on split-testing subject lines perfect reduces open rates by -28% and the most mediocre adjective good reduces open rates by a not-so-good -20%. Also watch out for wonderful which is... uh... less than wonderful.

Days of the week

According to Alchemy Worx, days of the week cause a drop in open rates. Especially Monday and Friday. This is probably due to the sheer volume of emails sent to promote Cyber Monday and Black Friday.


Mailchimp has found that donate is a big loser for open rates. Help and assistance are also to be avoided. However in slightly more heart-warming news, fundraising is fine. 


Using numbers may help quantify your message, but constant sales and promotion emails can lead to fatigue. Mix it up as much as you can.

Tired internet slang

If it hasn’t dated already, chances are for some people it already has: bae, fleek, dat, basic, derp, cray-cray, ftw, yort, AF, flex...

I have so may negative feels towards the above. I also may have made one of them up.

Oh and hashtags serve absolutely no purpose in email subject lines. In fact they may even hinder a recipient's ability to search for your email.

Deceptive familiarity

FWD: and RE: the artificial adding of ‘Fwd:’ or ‘Re:’ to trick you into thinking this is part of an ongoing conversation you’re engaged with already only creates distrust.



Content marketing

According to Adestra, content marketing headlines that use report (-23.7% opens, -54.8% CTR) and webinar (-16.6%, -70.7%.) fail to live up to expectations. As do the words book and learn, you uneducated lot.

Video, news and bulletin do work well though. As does the word 'content' itself.

Erroneous personalisation

Personalisation means nothing if your data isn’t correct and you don’t have 100% confidence in it.

“Paul check out these amazing offers!” when my name is Christopher, or even worse “[test] check out these amazing offers!”

In fact using a person’s name doesn’t really impact the open rate anyway, and can come across as needy or begging.

Punctuation shame corner

All of these…

  • Exclamation marks – the more there are, the less likely I am to open it.
  • Stars, squiggles, indistinct shapes – basically anything that isn’t actual text.
  • Hearts – bleuggh! 

[Putting anything in square brackets] or <these guys> immediately makes you think there’s been a coding error.

Although just to add balance, I did learn that travel site Travelocity achieved a 10.7% lift in unique opens by using a little airplane in its subject line. Which proves that relevancy to content and uniqueness is imperative to proper symbol use.

However, just remember that symbols appear in some email clients but not others, so it may just be a waste of time anyway.

Which leads me to the subject you've all been waiting for...


David Moth covered emojis in emails earlier in the year, but I shall condense the hard-hitting research here.

Pointy finger, sunshine and the number 10 are all bad according to Alchemy Worx. Snowman ftw though! Sorry I broke my own rule there.

The question of why the black sun increases open rates by 20.95%, while the white sun causes a drop of 8.03% has yet to be answered.

Other personal grudges

Awesome: Just stop using it. Everywhere. At all times.

TBT: so bored of 'throwback Thursday'.

I could probably end this article with a torrent of of all the different swear words I know, but being as I have no proof that these would negatively impact open rates, it wouldn't be scientifically correct to do so.

Further reading

For more on the proper use of email subject lines, check out these vital blog posts: Email marketing subject lines best practice, six case studies and an infographic on how to write effective email subject lines and 152 killer keywords for email and 137 crappy ones.

Christopher Ratcliff

Published 25 June, 2015 by Christopher Ratcliff

Christopher Ratcliff is the editor of Methods Unsound. He was the Deputy Editor of Econsultancy. You can follow him on Twitter or connect via Google+ and LinkedIn

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Comments (15)

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These are all pretty obvious but it's nice to be reminded that our prospects are neither dumb, nor do they want to be jerked around. Thanks!

about 4 years ago


Paul Devlin

Given the lack of education on this subject, I would imagine that there are many businesses making these mistakes every day. First ask yourself "How would you approach a stranger?" Thanks foir all of the research here, Christopher.

about 4 years ago

Pete Austin

Pete Austin, Founder and Author at Fresh Relevance

Modern email clients often show the pre-header (normally the first few words of email content) alongside the subject line in the in-box, so similar advice will apply to that too.

See here for a screenshot:

about 4 years ago

Joe Hawkes

Joe Hawkes, Senior Digital Marketing Executive at Charles Russell Speechlys

A lot of this supports the simple rule I use to write subject lines. It goes something like:

"Don't write what the recipient has to do, write what they will get"
"Don't write the action, write the result of the action"

I.e. the bad examples you use: 'Shop early', 'Book', and 'Donate' don't work as they tell the lazy and time-pressed recipient that they will have to take further actions once the email is opened, without telling them what they will get for their troubles.

about 4 years ago


Luiz Centenaro

Some of these may be obvious but it's a fantastic reminder, we have been analyzing eCommerce emails for years and over 80% of companies still push sales emails regularly.

Very few deliver value through email by sending great content or telling stories.

Posts like these help change that so thank you.

about 4 years ago


Phil Stevenson, Ecommerce Lead Designer at Personal

Good points Christopher and thanks for the article. I'd say everything needs to be tailored for your customer and tested.

Mailchimp might be off the mark a little as our '% off' subject lines have the highest open rates. That might be that we have a high number of sale shoppers in our database but everyone likes a bargain.

Personalisation should be pretty straight forward, although I get emails all the time with broken personalisation. Most email clients can handle if/and/or operators so if you don't have a first name you can use Title, Surname or just Hi.

We've been testing personalisation in the subject line, extended subject line, in the body and none at all; subject line wins by a mile.

Your quote by Parry Malm reminded me of an article on 'The Nudge Effect'

about 4 years ago

Parry Malm

Parry Malm, CEO at Phrasee Ltd.

Ooh, subject line language. Fun!

A few points:

1. Subject line language has a very small effect on spam boxing. 10 years ago it had a huge effect, but not anymore. The vast majority of deliverability issues these days stem from delivery infrastructure and domain reputation.

2. There are no words to avoid, and there are no words to always use. You must bear in mind the concept of "entropy" - originality and unusualness can be a strong factor to increase response rates.

3. Individual words aren't good or bad. Humans don't interpret language on a word-by-word basis. What you need to look at are high-order interactions between different language elements. The real driver of response is the emotional triggers held within a chunk of language, not changing "good" to "great" or something.

I've spent the last year deeply analysing subject lines and have come to the conclusion that individual word changes have a minor effect on response rates... and it assumes there is no interdependence between variables. Which is inrobust.


about 3 years ago

Christopher Ratcliff

Christopher Ratcliff, Editor at Methods Unsound / Search Engine Watch

@Parry - Thanks Parry. I knew I could count on you for the level-headed science bit.

about 3 years ago

Pete Austin

Pete Austin, Founder and Author at Fresh Relevance

@Parry - my feelings exactly. Do you have that somewhere I can link to it? Otherwise I'll probably reblog it with attribution.

about 3 years ago

Parry Malm

Parry Malm, CEO at Phrasee Ltd.

@Pete it's all built into our sentiment analysis tool. Happy to give you a run-through sometime. But in the meantime, just attribute it to Phrasee and that'll do for now :)

Huh. That would make for an interesting blog on Econsultancy. Maybe I'll start drafting one up, all I need now is time...

about 3 years ago


Phil Monk, Email Campaign Planner at Essentra Components

I got an email from Econsultancy this morning: Re: How integrated are your campaigns?

This wasn't part of an ongoing conversation, a reminder yes, but not a reply to an email.

Perhaps direct the person who wrote that subject line here :)

about 3 years ago

Graham Charlton

Graham Charlton, Editor in Chief at ClickZ Global

@Phil. Thanks, we'll have them thrashed.

about 3 years ago

Peter Leatherland

Peter Leatherland, Online Sales Manager at Ethical Superstore

@Graham & @Phil - looks like they are at it again today: "Re: What are you doing to improve conversion rates?" in my inbox today!

almost 3 years ago


Dorrey Smith, CEO at Comorosa

I'm so glad that I found your article Christopher! I'm a user of GetResponse platform and now I know which words I have to avoid in my emails to customers of my shop.

almost 3 years ago

Irwin Myers

Irwin Myers, President at Video One Productions

These ideas are well worth reviewing when preparing an email marketing campaign when just the smallest oversight or mistake can cause your efforts to tank. Thanks for the review of ideas.

over 2 years ago

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