The top 100 US retailers by e-commerce revenue sent recipients an average of 177 emails apiece, up 87% from 2007. Some of the most aggressive emailers—including Neiman Marcus Group Inc.—sent each recipient more than 500 emails apiece in 2011.

But some retailers have begun pulling back, reducing their mailings and fine-tuning their marketing tactics.

[See research in Wall Street Journal]

Open rates are falling: in the first six months of 2007, consumers opened 19% of the retail emails they received and clicked through to the website 3.9% of the time. By the first half of 2011, those numbers shrank to 12.5% and 2.8%, respectively.

Strategies to combat this?

Gamestop has split its customer base into two groups: general and rewards members. Over the last year, it has halved the number of emails it sends to general subscribers who may not be regular shoppers, focusing instead on its rewards program. Members of the rewards program typically open more than 30% of the Gamestop emails they get, compared with less than 10% for general subscribers.

In 2010, Neiman Marcus began using customer data to tailor its emails. It uses online purchase history, in-store purchase history linked to its credit card, and tracked online behavior to learn what brands, categories and types of deals customers favour - these then get targeted.