Want your email opened? Try sending it on Sunday at 3 p.m.—but brace for backlash

That’s according to recent research which found that the best time to send internal emails is on a Sunday between 3 p.m. and 6 p.m.

After studying 8.7 million emails, the communications software company Axios HQ found that those sent during that time frame had a 94% chance of being opened, compared with a usual 50 to 76% chance of being opened during the rest of the week.

Meanwhile, the second most effective time to reach your team is on a Sunday from 6 p.m. to 9 p.m., the researchers said, when emails have an 86% open rate. 

Messages sent during these times benefit from “low competition” because they aren’t fighting for workers’ attention with Monday morning meetings and the steady stream of emails that follow.

But don’t conflate employees’ responsiveness with happiness: Although emails sent on Sunday afternoon have a better response rate than on a busy working day, they’re unlikely to yield a positive reaction.

Prior research warns weekend emails are the worst—if you care about workers’ mental health

Tech has become increasingly intrusive in people’s lives outside of the workday, and prior research has shown that workers are struggling to switch off and getting Sunday night anxiety because they’re always contactable. 

Dr. Matthew Davis, associate professor at Leeds University Business School, calls this modern phenomenon “techno invasion.” 

He told the Times (U.K.) that it’s “linked to people feeling more stressed, less satisfied with their work and their work-life balance.”

“My worry would be if people see this and think, I’ll start sending these more routinely on a weekend,” he added. “Because for some people, it’s fine…but there is a good proportion of people [for whom] this will add to that sense of a burden.”

Dr. Laura Giurge, assistant professor at the department of psychological and behavioral science at the London School of Economics, echoed in her 2021 report on out-of-hour emails that they’re likely to make workers feel like they have to work all around the clock.

“Senders underestimate how stressful off-hour emails are for receivers,” she wrote. “Put differently, when we look at our inbox as senders, we seem to underestimate the impact that our off-hour behavior can have on others’ well-being.”

But it’s clear from Axios’ research that people probably already know that sending an email on a Sunday evening won’t land well with employees or peers because the data shows that they generally avoid doing so except in emergencies.

Despite its quick response rate, the weekend is the least popular time to send emails: The researchers found emails sent on a Saturday and Sunday are typically “essential communications” and account for a minuscule 2% of emails sent that week.

There’s a difference between being opened and being read

The report also highlighted that there is the risk of an email being opened, but then ignored because of employees’ annoyance at the timing of the note.

“Send windows do not always equate to reading windows,” the researchers admitted while adding that the percentage of employees who opened the email does not reflect whether it was properly read or responded to.

Ultimately, managers who genuinely need a response to an urgent email should take Giurge’s advice and clearly state that in the subject line of their email. “To help others protect their well-being, it’s important to clearly define the time frames of our requests,” she stressed.

Likewise, those sending non-urgent emails on a Sunday should also clearly state so to benefit from the quick open rate without impeding on workers’ well-being.

A version of this story was originally published on Fortune.com on August 4, 2023.

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