In the days leading up to a holiday weekend, consumers are increasingly tuning out email messages more often than usual, says Len Shneyder, vice president of industry relations at email marketing vendor SendGrid. That’s why the peak email-sending days for retailers’ email marketing messages shifted to the Labor Day itself this year, from Thursday and Friday a year earlier.

“Thursday is the new Friday,” he says. “Everything cools down. Many consumers don’t go to work, and they act as if it’s already the weekend.”

Because Labor Day is traditionally a holiday weekend that consumers spend outdoors and away from email, retailers appeared to adjust to lower engagement rates by sending 2.1% fewer emails during the Labor Day weekend 2018 than they did during weekends in the previous 30-day period.

With those trends in mind, retailers need to be strategic about when and why they send emails during a holiday weekend, Shneyder says. For example, if the peak email volume days were Thursday and Friday last year leading up to Labor Day, a retailer might beat the rush and send their main promotional message earlier in the week.

“There’s no need to fight for attention,” he says. “A retailer that strategically sends emails can beat the competition.”

That requires a retailer to pay heed to consumers’ actions. After all, sending an email too early in the day may cause the merchant’s messages beneath other senders and other messages. Peak engagement hours are consistent with normal weekends. Most people aren’t waking up at 6 a.m. checking their email before and at work on the weekends. Engagement begins to climb around 9 or 10 a.m. Mountain Daylight Tme and peaks between 2 and 3 p.m.

And with retailers’ email volume rising, that’s increasingly important. Compared with the weekends leading up to Labor Day, emails sent during the holiday had a 2.1% fewer delivered emails, 1.2% fewer clicks and 4.3% fewer opens.

However, those rising email volumes haven’t had a negative impact on the effectiveness of email marketing: Internet Retailer’s soon-to-be-released 4th-annual Digital Marketing Trends report finds that 31.8% of retailers cited email as the marketing channel that offers the best return on investment among marketing channels, nearly three times the percentage who cited the next-most cited channel, social media (11.8%).

“The good thing about email is it is highly measurable,” he says. “You can see how many emails you sent, how many were opened and tie those results back to ROI.”

Going into the Christmas and Hanukkah holiday season, retailers should be experimenting with their emails to find the ideal cadence and the messages that resonate with specific customer bases. For instance, a message offering a 30%-off discount on a shopper’s next purchase might work for frequent customers but may not work for more irregular shoppers. “Now’s the time for retailers to find their sweet spots,” Shneyder says.

SendGrid’s data is based on its analysis of more than 74,000 clients.