Most retailers in the United States waited until after 6:00 AM Eastern Time to send their first email on Cyber Monday this year, according to data from Bronto Software.

The report was based on 2015 Cyber Monday data from more than 400 US retailers as well as data from 2011 - 2014.

The hour between 7:00 AM and 8:00 AM ET was the busiest time for sending Cyber Monday emails, with 11% of retailers messaging consumers during that period.

There was also a flurry of emails sent between 4:00 PM and 6:00 PM ET as retailers tried to entice shoppers with last-minute offers.

A number of the retailers examined sent emails between 12:00 PM and 2 PM ET, a trend that Bronto had not seen in previous years.

More than half (52%) of the retailers examined sent more than one email on Cyber Monday this year.

About the research: The report was based on 2015 Cyber Monday data from more than 400 US retailers as well as data from 2011 - 2014.