Retailers sent 22.8% more e-mail marketing messages in the third quarter of 2013 than they did during the same period last year, according to a new report from Monetate. But the provider of e-commerce personalization, testing and analytics technology says that revenue stemming from those e-mails dropped 17.7% year over year in Q3.

The company’s latest edition of its Ecommerce Quarterly analyzes a random sample of more than 600 million online shopping sessions using the same retailers this quarter as in the third quarter of 2012. Monetate did not say how many retailers it analyzed.

The report found that e-mail accounted for 2.92% of traffic to retailers’ sites in Q3, down from 4.03% in the same period last year.  Monetate says the drop stems from Internet service providers weeding out e-mail they deem unwanted by looking at factors like inactive users, bad addresses, spam complaints and sender authentication.

The report also found that retailers’ average order value for purchases stemming from e-mail increased year over year by 7.55% from $93.43 in 2012 to $100.48 in 2013 during the third quarter. That compares with a 26.13% increase in average order value for social media and a 20.38% year-over-year increase for search marketing.

Nine retailers in the Top 500 Guide list Monetate as providing their personalization technology and services.  The company ranks eighth among personalization providers in Internet Retailer’s Leading Vendors to the Top 1000 E-Retailers guide.