Customers to retailers: ‘Don’t spam me, bro!”

February 7, 2013, 5:16 PM UTC

FORTUNE – How many flash sale emails a week does it take to drive a customer bonkers? Ten? Twenty? Fifty? It looks like retailers are pressing their luck.

In a January study conducted online by YouGov, a whopping 75% of respondents of the 2,000 people surveyed online said that they are overwhelmed by retailer’s emails and are turned off and resentful about receiving them. Given that many consumers don’t want to be bombarded online, how are retailers responding to their backlash?

In 2012, top retailers sent out an average of 210 promotional emails to their customers, according to the Retail Mail Blog, which tracks email campaigns of leading companies. Consumers are suffering from email fatigue.

Disgruntled consumers can always unsubscribe, notes Simms Jenkins, who runs an Atlanta-based marketing company and is author of The Truth about Email Marketing. But even after an onslaught of unwanted emails, some still welcome that one message offering a two-for-one deal they can’t live without.

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Email acceptance is often contingent on timing. Apple (AAPL) customers may ignore emails for six months until they want to buy a new iPad. Many consumers “emotionally unsubscribe until you deliver that email that gets them to buy,” Jenkins says.

As many consumers gravitate toward mobile devices, email effectiveness depends on subject headings and “soft” sales, like offering benefits such as free shipping. Many retailers have also adopted targeted marketing tactics to avoid annoying customers to the point that they resent their brands.

Retailers need to spend more time sending “clear benefits to … subscribers” and avoid just selling, selling, selling. “If you forget the subscriber, you’ve done a poor job,” Jenkins says.

At ecommerce deals site, consumers began to resist emails in 2008, says founder and CEO Jason Goldberg. Deluged by an assortment of daily deals and flash sales, consumers grew exhausted. Fab needed to reinvent how it communicated with its mostly Generation Y clientele. “What does Fab look like when emails aren’t the primary vehicle?” Goldberg says he wondered.

Fab opted to customize its emails based on user preferences, working with Sailthru, a New York-based company, which helped optimize its marketing campaigns. In fact, Fab sends targeted emails on sales for products like pet accessories, kids’ furniture, and toys to customers that request them. When Fab’s system discovers that an individual consumer hasn’t opened four or five of these emails, they are removed from that particular email list. The company’s email system uses algorithms that send customers messages based on their open and click rates, Goldberg says.

In September 2011, 75% of Fab’s daily web traffic came from email blasts. By January 2013, emails produced fewer than 25% of its customers and mobile traffic via iPhone, iPad, and Android apps generated 35% to 40% of daily traffic.

“We focus on quality, not quantity,” Goldberg says. Fab consumers are repeatedly asked if they want to stop receiving targeted emails.

Moreover, Fab strives to make its emails relevant and punchy, without offering deals or coupons. “We only try to send emails that we think our customers want. Our No. 1 rule here is to only send emails that you yourself would want to receive,” Goldberg says.

Online retailer (which is now owned by Amazon (AMZN)) has learned a similar lesson. Senior marketing manager Michael Fellner says that personalizing emails is the most productive way to making sure consumers respond. “The more the content speaks to you, the more likely you are to open and click,” Fellner says.

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To that end, Zappos studies its consumers’ browsing behavior when sending emails for about 70 of its different sales’ campaigns. It uses analytics, some based on third-party software and some proprietary, to determine its customers’ preferences and tailor their messages. If a consumer has browsed for running clothing or shoes in the past, for example, it sends appropriate emails, notifying them about new running products.

Zappos’ system is constantly scrutinizing and evaluating consumer behavior. “We’ll see how many people opt out and watch carefully how people react to our communication,” Fellner says. But that’s not the whole story. “You have to look at more than one metric. It’s a combination of factors, including gaining permission, the content, and other factors,” Fellner says.

While consumers may feel overwhelmed, emails from retailers are here to stay. Emails are “ingrained in every part of our life. Most people check them in the morning. You can delete them, archive them, but they’re tough to ignore,” says DJ Waldow, co-author of The Rebel’s Guide to Email Marketing.

With the analytical tools at retailers’ disposal, though, “there’s no excuse for a retailer not to know” what consumers want, Waldow says.