It had been emailing some customers up to 10 times a week with information including generic updates, highlights from specific designers and details of new products.
The company now sends each user two automatically generated emails a week that take into account their specific interests and preferences. Product update emails achieve a conversion rate of more than 10% and newsletter emails are opened by nearly half of recipients.
Martin Bartle, head of marketing at Net-a-Porter.com, said: "Lyris has enabled us to target customers based on their personal preferences making our communications more relevant and targeted."
The company sends out around 300,000 emails a week. Email drives 32% of Net-a-Porter's sales and generates more than £1m in revenue each month.
Lyris was recently shortlisted for a Revolution magazine award for its Net a Porter work.