Email volume predictably grew in 4Q13, thanks in large part to holiday mailings, according to a recent report from Yesmail Interactive.

However, volume and subscriber activity rate increases were accompanied by overall open rate and click rate declines.

Messages from insurance firms had the highest average open rate (25.7%) and total click rate (7.8%) in the quarter, Yesmail found. Emails from technology companies had the lowest bounce rate (1.1%), but also the second-lowest click rate (1.6%).

In 4Q13, both desktop and mobile click-to-open rates registered a decline of 2.7% and 5.7% respectively, due to opens increasing at a much higher rate than clicks.

Below, additional key findings from the report.

Mobile Growth

• In 4Q13, 55% of email opens and 37% of clicks happened on a mobile device, accounting for a 13% increase in mobile opens and 16% increase in mobile clicks between June and December 2013.
• Mobile revenue generated by email in 4Q13 went up by almost triple the rate of desktop revenue (52% vs. 18%), and growth in mobile conversion rate outpaced desktop conversion rate by more than two to one (23% vs. 11%).
• The number of mobile orders generated by email went up by 58% in 4Q13, and accounted for over 18% of all orders placed as a result of a marketing email, a 13% increase over 3Q13.
• 59% of all mobile orders driven by email were completed on a tablet.

Subscriber Tenure

• Engagement for new subscribers increased 20% in 4Q13, but, unexpectedly, the overall number of newly acquired subscribers went down 11%.
• Engagement for the mature subscriber segment (opted in 3-12 months) increased 7%—and 6% for subscribers with more than a year of database tenure.
• On average, only 14% of all subscribers have been active (opened/clicked) in the last year.

Activity by Provider

• Of the four major Web-based email service providers—Gmail, AOL, Yahoo, and Hotmail—Google's offering has the most active subscribers.
• 19% of Gmail subscribers have been active within the last year, compared with 10% for AOL, 12% for Hotmail, and 14% for Yahoo.
• Gmail users also accounted for 43% of all new subscribers in 4Q13—up from 39% in 3Q13.
• AOL had the largest base of subscribers in 4Q13 who have never been active (79%).

About the research: The report was based on data from 6.4 billion marketing emails sent in 4Q13.