The Best and Worst Email Subject Lines in 2013

A detailed survey of over 2.2 billion emails, published this year, has revealed the most (and least) effective keywords and phrases in email marketing subject lines. 


It’s not unheard of for marketers to spend hours constructing great emails, only to treat the subject line as an afterthought.

What makes a good subject line?

Much like the broader web, email is now all about usability. The subject line is one of the main things within a marketer’s control to influence customer behaviour. An ambiguous subject line delivers a poor user experience. Conversely, a strong, effective subject line drives short and long term response rates.

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The Email Subject Line Analysis Report 2013 was written by Parry Malm.

Don’t get lost in the shuffle

More emails are being sent out than ever before. As many as 144 billion per day, according to a Mashable report last year. With all these digital messages landing in inboxes, subject lines have to be attention-grabbing, in order to avoid emails being summarily deleted without opening. Here are some quick tips to increase open rates.

Overall keyword performance

Words like ‘Exclusive’, ‘Offer’ and ‘Save’ had a high open rate, but a low click rate and a high rate of unsubscribes. ‘Free delivery’ achieved 50.7% open rate variance on average, but also 82.4% unsubscription rate variance.

Terms relating to timing or recency largely did well. ‘New’, ‘Alert’ and ‘Latest’ were good performers. ‘Monthly’ was a bad performer, with low clicks and high unsubscription rates, but ‘Weekly’ was an excellent performer, with high opens and low unsubscription.

Of the keywords relating to content, ‘Video’ was by far the best performer. Traditional terms like ‘Newsletter andReport’ were poor. But the oh-so-modern ‘Webinar’ performed even worse.

Email Subject line overall

Retail and Ecommerce

Forget ‘Cheap’ and forget ‘Free’. Both of these saw dire open and click-through rates. ‘Birthday’, ‘Christmas’ and ‘Holiday’ did badly too,with the latter returning an 88.2% unsubscribe rate compared to industry average.

Sale’ fared better on clicks and opens, while ‘Free delivery’ was one of the better performing titles in the generally depressing retail and ecommerce category.

(24 terms in total were analysed in this category)

Email subject lines retail ecommerce

B2B Publishing

For B2B publications, ‘Review’, ‘Update’ and ‘Special’ all test well, indicating an interest in added value and expert insight. Open rates on contest and competition emails were low, but clicks were higher than average, even for ’spammy’ words such as ‘Win’.

Newsletter’ did better in the B2B sphere, with ‘Video’ and ‘Limited’ also getting higher clicks and opens.

(22 terms in total were analysed in this category)

Email subject lines b2b publishing

B2B Events

Trying to get professionals to attend a trade event? Not all keywords will do the trick. Many of the ‘incentive’ terms, like ‘Early bird’, ‘Last chance’ and ‘Offer’ did badly. ‘Exclusive’, ‘Invitation’ and even ‘Download’ performed well across the board, with high opens and low unsubscribes.

(29 terms in total were analysed in this category)

Other sections in the report:

  • B2C Events

  • B2C Publishing

  • Charities

  • Subject line strategy

  • Split testing


The research took a random sample of over 90,000 email campaigns, each with a minimum list size of 5000, analysing a total of over 2 billion emails.

Download a copy of the Email Subject Line Analysis Report 2013 here.

Which subject lines work best for you?

email subject lines b2b events

Comments: 1

  • Jay says:

    Interesting case study I was not surprised to hear that the term free shipping produced a very high open rate and the word free saw a decline since that word sometimes triggers a red flag with some spam filters.

    Good tips I am going to be using some of your tips in my next email marketing campaign thanks:)

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