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Adestra study of almost 1 billion emails shows specific words to boost response

Latest research shows subject line length and specific words and phrases can make or break your email marketing campaigns.  Subject lines are often overlooked and yet can have a massive effect (both positive and negative!) on response rates for brands’ campaigns – something marketers should be testing regularly. Adestra has analysed nearly one billion emails to establish what works for four key sectors, as well as B2B vs B2C, with some fascinating results.

Report author, Parry Malm, Account Director at Adestra says: “Our new subject line research has produced some incredibly interesting stats. It’s only one aspect of your email marketing arsenal, but when approached in the correct way subject line optimisation can prove to be an effective, and quick, tactical winner to help drive response rates.”

The report covers 6 sectors:


With the ecommerce sector, character and word count results are paradoxical. The choice is clear – shorter subject lines drive clicks, and longer subject lines drive opens. Marketers need to consider their objectives and then construct subject lines accordingly. Subject lines with 70 characters also appear to provide a huge uplift in click throughs. “˜Coupon’ and “˜voucher’ are out and “˜% off’ and “˜Summer sale’ are in – if you want to drive both opens and clicks.


The best click through rate comes from 15 words/120 characters upwards. Focusing on the benefits of attending a given event – be it the exhibitors, speakers, show features or whatever makes the show special.  The words “˜conference’, “˜seminar’ and “˜webinar’ have much less impact than selling the benefits in the subject line. Mentioning price, discounts or using currency symbols can create a big uplift. Personalisation is also important here.


For publishers, the results are quite clear – a higher word count delivers more opens and click through rates. Similar to the events sector, sell the benefits and give more information about what your email contains, and your responses will increase. “Newsletter” or “Forecast” or “Intelligence” are to be avoided, while “Bulletin” or “Alert” will see your rates increase. Use cutting edge content – “Exclusive”, “Video” and “Interview” are all good.


Short subject lines drive both opens and response. If it’s a donation campaign then this is critical! However, if it’s an awareness campaign then longer subject lines will drastically improve open rates.

The words “˜appeal’ and “˜donate’ have lost their, well, appeal with recipients. Going back to basics with “˜give’ can increase results dramatically. If you want to increase your opens by 41% mention “˜kittens’, but it will drop 28% if you mention “˜children’ – strange, but true!

B2B vs B2C

Quite simply, the more words the better for the B2B sector – anything over 16 words however can deliver on both opens and clicks. For B2C, a 20 word subject line appears to be clear winner, delivering a massive 115% uplift in open rates and 85% uplift in clicks! Be clear about what your email is about and the trust of your recipients will follow. Money talks in the B2B sector, with subject lines containing monetary symbols, monetary phrases such as “turnover”, “revenue” and “profit” achieving fantastic results. Avoid “B2B”, “Business” and “industry”.  Video content rules in the B2C sector, with the word “video” boosting open and click through rates dramatically. Avoid “free and “half price”, opt for “% off” instead and see the positive impact this makes.

For a full copy of the report click here >

The study took a random sample of email campaigns, each of which were delivered to more than 5000 recipients, giving a total volume of 932 million emails sent over a six month period.

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