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

The report, which was based on data from 62,000 US newsletter campaigns sent in 2013, found that emails arriving on Monday had a 12% average open rate in the first half of the year and a 12.9% open rate in the second half.

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

The weekends accounted for the lowest open rates in 1H13, with 9.9% on Saturday and 10.3% on Sunday. In the second half of the year, the lowest open rates occurred on Sunday (9.6%) and Thursday (11.5%).

However, though open rates were relatively low on Sundays, clickthrough rates were high. Sunday had 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 rate in 1H13 (1%); Monday and Wednesday tied for the lowest rate in 2H13 (1.7%).