I run Alchemy Worx - a digital marketing agency with a 100% focus on email, and our findings are based on analysing over 600 subject lines and 200 million email messages and believe that this research disproves (PDA’s aside) the widely held view that short email subject lines are better.

We discovered that although subject lines with 50 characters or less make more people open the email - the traditional view - they are less likely to then go on and click on content or offers within the message. The study found that the click-to-open rates start to be optimised when the subject line is over 70 characters in length and continue to rise until well beyond 100 characters.

This is true for both the number of characters and the word count. The more words there were in the subject line, the better the click-to-open rate.

One of the most common questions I am asked at conferences is what subject lines work best, so I am delighted to discover this rule of thumb.
In the last eight years of working on our clients email marketing programmes we amassed plenty of circumstantial evidence that suggested longer subject lines could be as, if not more effective than shorter ones, so we commissioned this research to find out once and for all.

In summary our findings show that:
- Short subject lines less than 50 characters long or containing less than 6 words optimise open rates

- Long subject lines – over 70 characters or 10 words optimise both click and click-to open rates

We were also surprised to identify a “dead” zone!

- Subject lines of between 60 and 70 characters (6-10 words), optimise neither the open rate or click to open rates.”

The white paper containing full results and analysis is now available as a free download
http://www.alchemyworx.com/subjectlines-lengthiseverything.php