Email newsletters that arrived in consumer inboxes on Monday had the highest open rates on average last year, according to a recent report from MailerMailer.

The report, based on data from 62,000 newsletter campaigns sent to the United States in 2013, found that emails arriving on Mondays had an average open rate of 12% in the first half of the year and 12.9% in the second semester.

Emails arriving on Tuesday had the second-highest average open rate in the first half of the year, and Friday took second place in the second half.

Weekends represented the lowest opening rates in 1H13, with 9.9% on Saturday and 10.3% on Sunday. In the second half of the year, the lowest opening rates were on Sundays (9.6%) and Thursdays (11.5%).

However, even though open rates were relatively low on Sunday, click-through rates were high. Sunday recorded the highest average CTR in 1H13 (2.2%) and tied with Tuesday for the second highest rate in 2H13 (2.1%).

Saturday had the lowest average click-through rate in HY13 (1%); Monday and Wednesday tied for the lowest rate in 2H13 (1.7%).

Below are additional key findings from The report.

Time of the day

• Emails are more likely to be opened earlier in the day, between 8 a.m. and 12 p.m. local time.
• Open rates on a typical day last year began to increase at 3 a.m., peaked around 10 a.m. (at 6.5%), then slowly declined over the post- noon and evening.

It’s important to note that these opening hours do not necessarily correspond to delivery times, as emails were often opened several hours (or even days) after arriving in consumers’ inboxes.

Subject line length

• Emails with short subject lines, between 4 and 15 characters, had the highest average open rate (16.8%), according to the analysis.
• Emails with longer subject lines had lower open rates on average.

About Research: The report was based on data from 62,000 US newsletter campaigns (1.18 billion emails) sent in 2013.