This year, 68 percent of the biggest online retailers sent at least one promotional email on Cyber Monday, making it the largest email marketing day of the year to date, a 44 percent rise over last year.

"I think one of the big reasons that it is up this year is that retailers are making a really big push to bring the retail sales early this year, because of the instability in the economy," Chad White, founder of RetailEmail.Blogspot and director of retail insights at the Email Experience Council, told DM News. "Retailers are using e-mail to help this."

Twenty-five percent of the largest online retailers sent at least one promotional email on the Sunday before Cyber Monday, which made it the biggest Sunday for email marketing this year, an increase of 12 percent over last year.

"It’s another selling occasion in the early core of the holiday season," White said. "Its close to Black Friday, so it is feeding off of it, and the term Cyber Monday is accepted by consumers, so they are more open to it."

Last year, Cyber Monday was the sixth busiest day of the year for online retailers to send emails. It was surpassed by two of the three Echo Mondays, Mondays after Cyber Monday but before Christmas. In December and the day after Christmas had the most retailers sending promotional email, at 53 percent.

"Last year, Echo Mondays saw a higher amount of e-mails, so we expect to see more e-mails on these Mondays this year," White said. "There is something magical about Mondays for retail sales during the holidays."