Ask any online retailer to name their most frustrating business challenge, and the chances are very good they will say it is shopping cart abandonment. Probably a 75-percent chance or better, which is exactly how high the abandonment rate itself has climbed — to 76 percent, according to the latest report from Forrester Research.

Strangely, while cart abandonments are costing e-commerce merchants nearly $20 billion annually in lost sales, the chances are also high that you know a retailer who does not attempt to regain these customers through an email retargeting program. Sixty-eight percent of merchants do not, according to a study by Econsultancy and RedEye, compared to just 32 percent who do have such a program in place.

When executed correctly, cart recovery emails generate an average of nearly $18 in revenue per message sent, according to research conducted by retargeting solutions provider SeeWhy. The study also showed that an average of 20.8 percent of cart abandoners go back to the site and buy something after receiving these targeted emails, and that they wind up spending 55 percent more than shoppers who made purchases without abandoning their carts.

“The revenue achieved by retargeting emails far outweighs the cost to implement these solutions,” says Heather Bonura, the director of brand strategy for email marketing services provider Listrak. “Not to mention that you’re building customer loyalty with every sale and engagement, so these retargeting solutions can increase customer lifetime value. And they’ve also been known to convert at a much higher average order value than standard site orders.”

Listrak’s cart abandonment email solution is one of several on the market today, but the company has established itself as one of the most aggressive vendors in the space by partnering with multiple e-commerce platform providers in the past year. Retailers utilizing platforms such as Magento, Volusion, Miva Merchant, 3DCart and X-Cart can deploy the Listrak email retargeting solution to automatically send one or a series of emails to cart abandoners with the intent of guiding them back to the site to complete their orders.

Additional email marketing service providers such as MailChimp, Campaigner, Constant Contact, Exact Target and others offer retargeting solutions as a way for merchants to reclaim sales otherwise lost to cart abandonment, yet the abandonment rates continue to climb and the number of retailers using these solutions remains in the minority. If you are a merchant who is dissatisfied with the fact that three out of four shoppers will abandon their carts before checkout, it may be time to rethink your own strategy for fighting cart abandonment.

Below are four proven best practices to follow when fighting cart abandonment through email remarketing:

Make it possible
Merchants cannot retarget cart abandoners through email if they do not have an email address. This is why getting that address in the first step of the buying process is so critical, and making it a simple, email-only “form” is the most effective way to accomplish this.

Act quickly
More research from SeeWhy has shown that 54 percent of all carts successfully recovered are regained within the first few hours after abandonment, and most vendors offer solutions that send automated responses in real time to within the first three hours. Average conversion rates for recovery emails that are sent immediately after abandonment are 11 percent, and that number falls to 6 percent after the first day and drops down to 3 percent after a week.

Sell aggressively
Plan to send a series of three emails, one in real time or within the first few hours of abandonment; the next (if necessary) two or three days later, and the third (if necessary) two or three days after that. The first message should be a reminder of the items left in the abandoned cart, and if that message does not result in a sale, the second message should include an incentive such as free shipping or 5 to 10 percent off the order. If a third message is still necessary to complete the sale, up the ante with a last-chance attempt by sweetening the offer to 15 percent off if purchased within the next 24 hours.

Test and tweak
Only through analytics, however, will you be able to identify any “serial abandoners” who try to gain these incentives by repeatedly ditching their carts. This makes it all the more important to you’re your messaging constantly and segment your email lists accordingly.