For as long as marketers have been sending out emails to prospects, they’ve wondered if they could improve their results by tweaking the day or time they send messages. While the debate about whether any of it makes a difference to open or click rates rages on, it can still be useful to look at what the data from a large sample size might reveal. In their annual report, MailerMailer released their findings from a study of over one billion opt-in email newsletters sent from US accounts.

Unsurprisingly, those emails sent out during traditional work hours and heavy commute times tended to have the lowest open rates. Of course, this doesn’t mean that these emails were necessarily opened around the same time they were sent. In fact, the emails with the highest open rates (those sent during evening hours) were most frequently opened during regular working hours.

While it may make the most sense on the surface to send emails at the time when the most people are in front of their computers, the study’s findings would suggest that daytime emails get lost in the shuffle. Whereas, sending your email the night before the subscribers use their email could place your message closer to the top of their to-read list.

For both open and click-through rates, emails sent between one and two in the morning seem to receive a bump in engagement that’s contrary to the rest of the data.

Of course, timing alone may not be sufficient to spur your subscribers to action. MailerMailer’s report further revealed a potentially disturbing trend. While email open rates are trending upward, click-through rates are on the decline. Although the rise of mobile devices for checking email could be to blame, since people don’t always click links on their mobile device because of poorly optimized sites, its impact on email habits remains slight.

As far as what day is best for catching subscribers in front of their emails, Sundays were found to have the lowest open rates, with Mondays far outperforming the rest of the week. Whether this means that Monday is the best day to send out a newsletter or that people are simply playing email catch-up at the beginning of the week remains unclear. Click-through rate data by day of the week is just as murky.

The study also shed light on how long it usually took for subscribers to open emails after they arrived in their inboxes:

  • 5% of opens occurred within the first hour
  • 4% of opens occurred within the first five hours
  • 82% of opens occurred within the first 24 hours
  • 90% of the total opens for an email occurred within the first 48 hours
  • Opens typically stopped occurring after the two-week mark.

When it comes to the click-through rates, the study revealed that having more links in an email led to a higher click-through rate. For example, emails with an excess of 21 links had CTs of 2.1%, a full percent higher than emails with fewer than five links.

It also bears mention that personalization can help to improve open and click-through rates. While a personalized subject line made little difference, the data showed that a personalized message improved engagement across the board. By ensuring that your messaging consistently provides content your subscribers care about while paying attention to which days and times your messages receive the most attention, it could be possible to finally maximize the usefulness of your opt-in email list.


MarketingCharts. US Email Open and Click Rates, by Hour Scheduled, in 2014. October 27, 2015.