Few retailers send more marketing emails than Neiman Marcus Group LLC Ltd. The multichannel retailer sends 64 marketing emails per month, on average, according to Internet Retailer’s Top500Guide.com. That’s more than all but nine of the 500 largest online retailers in North America and 276% more than the 17 per month average across all 500 merchants.

There’s good reason for that volume: Email works, says Jeff Rosenfeld, the retailer’s vice president, customer insight and analytics. Over the past year, it has driven roughly 5.5% of NeimanMarcus.com’s desktop traffic, according to SimilarWeb Ltd. That traffic comes at a relatively low cost, given that it costs little to send email.

It isn’t just Neiman Marcus that continues to find email an extremely effective marketing channel; 38.7% of online retailers in Internet Retailer’s second annual Digital Marketing Survey said email offered the best return on their investment among 10 marketing channels, making it the clear leader over the next most-cited channel, social media, which 16.1% of respondents named.