The latest figures from the Retail Email Index have shown another increase in email marketing activity among US retailers.

According to the index, email activity surged by 11 percent in the week ending November 21st compared with the previous week – when email campaigns also increased – to reach 272 points.

Each of the top 100 internet retailers sent an average of 2.7 different promotional emails last week, while more than half of these messages made a reference to Christmas, according to the Retail Email Blog.

Monday was found to be the day on which the most emails were sent, while other common references in promotional emails included those to winter sports, toys, cashmere and holiday parties.

The Retail Email Blog said: "It’s very likely that Monday will be the most popular day of the week to send emails until the end of the year."

Huw Griffiths of Campaigner told last month that business-to-business email marketers would do well to take advantage of the Christmas period to reinforce their brand in the minds of customers by sending them thank you and season’s greetings messages.