The marketing platform Retention Science analyzed over 1 billion emails sent in the past two years to pinpoint what types of emails incite higher engagement rates. The company claims that the emails were representative of a cross-section of retailers and brands, and were normalized to account for various sample sizes.

The Holidays Are Key for Email Marketers

Email marketers preparing for the holidays should take note that click rates are highest in October (30%) and November (27%), according to Retention Science. Unsubscribe rates are also at their lowest in November (4%) and December (5%).

Retention Science states that this is likely because consumers are on the lookout for deals during the holiday season. Indeed, emails with percent-off deals are 38% more likely to be clicked.

Consumers are most likely to unsubscribe from emails in August (28%).

Subject Lines Should Be 5 To 10 Words

Shorter subject lines directly correlate to an increase in open rates, according to the report.

Email subject lines that range from six to 10 words have the highest open rates (21%) overall, while subject lines with five words or less followed closely behind (16%).

Retention Science states that open rates dramatically fall when subject lines are over 10 words. Subject lines ranging from 11-15 words have an open rate of 14%, while subject lines ranging from 16-20 words have open rates of 12%. Emails with subjects of 20 or more words had the lowest open rate overall (8%).

This is mostly likely tied to mobile, as more than half of all emails are now read on a mobile device. Many email providers, such as Gmail and Outlook, even limit mobile subject lines to a certain number of characters.  

Marketers should condense longer subject lines to ensure that their wording is not cut off when being read on a mobile device or application.

Email Etiquette Matters

Punctuation also affects email open rates and increases open rates by 9%, according to Retention Science. The study also reported that subject lines with question marks are 44% more likely to be opened than emails with exclamation points.

78% of consumers say email etiquette has an impact on their decision to engage, according to a recent study by Fractl and BuzzStream.

FoxType Labs recently released an online etiquette tool for email marketers interested in checking the tone of their emails.

The new tool analyzes sentence tone and structure to grade emails on a scale of 1 (impolite) to 100 (polite). The company aims to help writers correspond in friendlier tones and offers a free Gmail plugin for users.