Secrets of Writing the Perfect Email

Secrets of Writing the Perfect Email via Gmail Boomerang

There’s a lot of advice about how to write a good email on the web, from adding more cowbell to general writing advice to full sets of pre-written email templates. But almost none of that advice shows the data behind it (we’re guessing because there isn’t any), and a lot of it contradicts itself.

So here’s the roundup of what really matters when you’re sending an email, and how much each factor matters.

Sentiment graph


Message length data
One of the most significant factors in determining response rates is how positive (words like great) or negative (words like bad) the words in the message are. Emails that were slightly to moderately positive OR slightly to moderately negative elicited between 5-15% more responses than emails that were completely neutral.

We would advise against both excessive flattery and writing hostile, day-ruining screeds. Poisonously negative emails were less likely than even neutral emails to get a response, and extremely positive emails did little better.


Subject length data
The sweet spot for email length is between 50-125 words, yielding response rates above 50%. While average emails from Jeb and Hillary clock in at 10 and 9 words respectively, unless you’re running for President, sending emails that short mean you’ll sacrifice about 30% of your responses. Response rates slowly declined from 125 word messages to 500 word messages, then fell faster after that. So if you need to send War and Peace, you might want to send it as an attachment!


Reading Grade Level Data
Email marketing veterans know that testing subject lines is a critical step in designing an email campaign that will have a high open rate. Likewise, the length of your subject line impacts response rates, and the optimal length is shorter than we expected. Subject lines with only 3-4 words (excluding email conventions like Re: and Fwd:) received the most responses. Including some sort of subject line is critical: only 14% of messages without any subject line at all received a response.


Question Data Subjectivity Data
Our most surprising finding was that the reading grade level of your emails has a dramatic impact on response rates. Emails written at a 3rd grade reading level were optimal, providing a 36% lift over emails written at a college reading level and a 17% higher response rate than emails written at a high school reading level.

The main components of reading grade level scores are the number of syllables in your words and the number of words in your sentences. So try using shorter sentences and simpler words than you normally would. You can check your content’s reading grade level in the Word Count tool in most word processors, or search for “Flesch Kincaid grade level” to find a multitude of online tools.

The number of questions you ask in an email has a sweet spot, just like the number of words you write. We found that emails that asked 1-3 questions are 50% more likely to get a response than emails asking no questions. But a bombardment of questions won’t help you either – an email with 3 questions is 20% more likely to get a response than an email with 8 or more!
If your natural writing style has a “just the facts, ma’am” bias, you should consider including more opinions and more subjectivity into your messages! The more opinionated the content of the email, the higher the response rate climbed. One caveat – we have no idea if those subjective emails generated positive responses or declarations of war, so caveat writer!

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