7 email subject line myths exploded

boom-hiIts no wonder that there’s lots of subject line advice around as subject lines really are so important to an email. In testing I’ve found the right subject line can double click rates, though more typically the uplift is a still welcome 25%.

The amount of subject line talk has meant many things are passed off as best practice but in fact are poor advice

Myth #1 Don’t use CAPITALs in subject lines

I believe this myth stems from the idea that capitals are shouting and its rude to shout, though another reason is that capitals are harder to read, the human eye can read lowercase faster. In many thousands of subject lines I reviewed I found only one in which the whole subject line was uppercase. In contrast the use of a few capitalized words in the subject line is relatively common.

Using capitals does help standout of the subject line and allows emphasis to be placed on key words. About once a month Miss Selfridge use a subject line that begins:


The rest of the subject line depends on their offers that month. As well as getting standout the frequent (but not too frequent) use of this capitalisation trains customers to know, recognise and expect it.

Over the Jubilee Ann Summers ran,

NeVer MiNd tHE MoNaRcHs?

which certainly stood out and played on the Sex Pistols album of almost the same name. Whilst the alternating upper and lower case make it initially hard to read, the standout buys the extra few seconds of the consumer attention needed to read it.

Myth #2 Subject line name personalisation makes the email look spam-like

The concern is not that the email gets filtered as spam but that it is tacky, spam like and tarnishes a brand. Marketing opinions on this are often strong both for and against.

The most common personalisation is to include the first name at the start of the subject line, for example…

“Sarah, Weekend Super Saver 15% off”.

In analysis it’s very rare to see a first name included anywhere but at the start of the subject line.

In tests including a first name often gives an increased response rate. Better subject line personalisation goes beyond just the name and tailors the whole subject line message to the person or segment.

Real world examples are, Travelodge and Cloggs.co.uk who start every subject line with the first name whilst Disney includes it on about one in four subject lines. Since using the exact same approach on every subject line creates boredom and customers can tune out from it, the Disney approach of varying the subject line style makes more sense. If you do see a split test uplift with use of first name, do re-test regularly to check its effectiveness is not lost.

Myth #3 Don’t use spam trigger words like Free in the subject line

This is probably one of the most persistent old wives tales when it comes to subject lines. That use of “free” gets you filtered to junk. Many years ago there was some truth in this, as at that time email was largely filtered based on content. The biggest spam filtering factor now is reputation, which itself is heavily based on spam complaints.

Content is now only likely to get you filtered to junk if your reputation is weak.

Go ahead and use free and other sales trigger words, even put free in upper case too. Keep an eye on the inbox placement and if you see a problem then cut back on the sales words and resolve your underlying reputation issue. Once resolved you can restore use of these words.

Myth #4 Judge subject lines by the open rate

If a subject line creates lots of opens but few clicks and conversions just how good was it really? For most commercial mailings open rates are a weak measure of marketing objective. Click, post click and conversion measures are better metrics, even when it comes to deciding on subject lines.

It’s not uncommon to see a lower open rate subject line generate higher click rates. This happens when the lower open rate subject line is a better qualifier. Fewer people may open; however those that did were the right people and were more likely to click, leading to high click rates overall.

Myth #5 Keep subject lines short

I’ve nothing against short subject lines. The problem is with short subject lines at the expense of meaning and clarity. If the subject line is so short the reader doesn’t know what the email is about then it loses effectiveness.

Take these two short lines from Ryanair, “Book Today” and “£5 Seat Sale”. The second one is better as it says something about the email content. In this example the £5 offer was limited to midnight on the following Monday (48 hours from when the email was sent). Given urgency is a strong driver it might have been worth using a longer subject line and including the cut-off date. As a further example, had the offer been around particular destinations then by adding those it would better qualify the openers.

By contrast this 154 character example from Dorothy Perkins “Floral prints, peplum shapes and flattering silhouettes – say hello to Zen Garden! It’s battle of the denim with DP vs. Cosmo, plus 30% off all jewellery”

Determine your message and then aim to say it succinctly. Thus concentrate on getting your message communicated not the number of characters.

Myth #6 The only point of a subject line is to get an open

Many customers read your subject line but don’t open your email. The subject line message still has impact even when an open doesn’t follow. It leaves an impression with the consumer.

Your brand values, product range and more can be communicated through the subject line, even to non-openers.

Myth #7 I know what works

Whilst guiding principles can be used to write good subject lines, we are not the best judges of the best subject lines. Customers are the best and split testing is both an easy and effective way of understanding just what customers think.

Split testing subject lines is one of the easiest optimisation wins. The win is not just to get an uplift on the current campaign but through analysis of subject line differences creating theories to guide future campaign subject lines. This  avoids re-learning on every campaign and enables on-going refinement.


Fundamentally, subject lines are attention grabbers that need to resonate with the reader. Thus the best subject lines are written when there is a clear sense as to exactly who the reader is, what they want, how you express what’s in it for them and ensuring the subject line is well aligned to the content of the email.

Footnote: I first published this article on Smart Insights