December 17, 2012
Email Subject Line Performance

As the marketing person at a SaaS startup focused on online cloud storage, OfficeDrop, I obviously experiment a lot with email performance, varying subject line, content, design, etc. Recently I came across a very interesting study showing email effectiveness, both by open rate and click through rate, by email subject line. Subject line is one of the most important pieces of any email campaign, and it’s very interesting to see data aggregated across a large number of campaigns.

The study was done by Adestra and is available here. Based on billions of sent messages from b2b companies, the study looks at the performance of different subject lines. I'm just going to quote from a solid Marketingchart write up on the study, as it is very interesting data (the following is a direct quote):

  • Currency symbols: Subject lines containing the £ symbol had a far better-than-average (57.8%) click-to-open rate. Those with $ signs scored above-average in opens (15.7%) and clicks (14.7%), but slightly below-average in click-to-opens (-0.8%). Subject lines containing the € symbol were above-average in opens (2.9%) but below-average in clicks (-8.2%) and click-to-opens (-10.8%). Of course, targeting has a big effect on this – as some symbols may be irrelevant to the recipient.
  • Discount terms: These generally performed below-average. “Sale” was the outlier, above-average in opens (14.4%), clicks (76.5%), and click-to-opens (54.3%). Others such as “% off,” “discount,” “free,” “half price,” “save,” “voucher,” “early bird,” and “2 for 1″ all came in below-average in all 3 metrics, save for “voucher,” which had above-average opens (6.5%). “Early bird” was the worst performer in terms of clicks (-71.6%) and click-to-opens (-67.6%).
  • News terms: These had better success than discount terms. “News” (16.2%), “update” (4.9%), “breaking” (33.5%), “alert” (25.9%), and “bulletin” (12.5%) all saw better-than-average click-to-open rates (as well as clicks and opens), with “newsletter” being the only term to perform below-average in each metric. “Alert” saw the best differential for clicks (78.3%), while “news” did best for opens (30.9%).
  • Content terms: There were more discrepancies in this theme. “Issue” (8.5%) and “top stories” (5.9%) were the only to perform above-average in click-to-opens, although the latter saw slightly below-average open and click rates. “Forecast,” “report,” “whitepaper,” and “download” all saw below-average performance in each of the 3 metrics. “Research,” “interview,” and “video” scored above-average for opens, but below-average for clicks and click-to-opens.
  • Benefit terms: “Latest” was the only to see above-average clicks (8.8%) and click-to-opens (9%), while “special,” “exclusive,” and “innovate,” while performing about average in opens, fared far more poorly in clicks and click-to-opens.
  • Event terms: Each of these terms performed below-average in opens, clicks, and click-to-opens. The terms examined were: “exhibition,” “conference,” “webinar,” “seminar,” “training,” “expo,” “event,” “register,” and “registration.” The worst offender for click-to-opens was “webinar” (-63.5%).
  • Multichannel terms: Facebook (21.6%) and Pinterest (16.4%) were the only terms to score above-average in clicks and click-to-opens, though both showed below-average performance in opens. On the flip side, “app” and “iPad” were above-average in opens, and below-average in clicks and click-to-opens. Both “Twitter” and “LinkedIn” were below-average in all 3 metrics.

A few of these are likely to be correct for many email marketers, regardless of industry of end customer. The low performance of words like "webinar" and discount terms is probably something most marketers will see with their email campaigns. Of course, testing pretty much any big email campaign makes sense!

Healy Jones is the head of marketing at OfficeDrop, and blogs at about marketing, mobile and venture capital.  You can follow Healy on Twitter (@HealyHoops) by clicking here.

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