• by Laurie Sullivan  @lauriesullivan, May 4, 2009

Encyclopaedia Britannica has been testing a feature in Silverpop's Engage that determines the best time to send an email to each recipient on a list based on his or her individual behavior.

The Send Time Optimization feature addresses a long-time challenge for email marketers -- identifying the best day and time to send email that will initiate a response.

Silverpop captures the times that people open the email, stores this information in a data field within the client's distribution list and keeps track. The time optimization feature does not rely on the last email, but the past several. If the times are different, it adjusts the target time to somewhere between. The more data collected, the better it works, according to Kassie Stephenson Adams, director of consumer marketing, campaign management, Encyclopaedia Britannica.

Encyclopaedia Britannica began testing the feature early in April. The company sends three types of emails, but chose to focus on the one highlighting products, such as a campaign introducing a new book on American History.

One to two emails sent weekly focus on product-specific campaigns related to the online store. Eight emails have gone out since the first on April 7. About five emails have been distributed with the time feature turned on. "I expected to see the open and click rate increase, but both remained unaffected," Adams said. "We noticed that the revenue rose between 40% and 60%, depending on the message."

Adams attributes the increase in revenue to the timing of the message. People were ready to make a purchase at that moment. Since online shopping has become more popular, people put aside a time in the day when they check all their emails, and this is why optimization works well, she said.

Bill Nussey, CEO of Silverpop, said the Atlanta, Ga.-based company has been working on the algorithms for about two years. Sending individual emails to recipients in a large list at a specific time has been the biggest challenge. It requires collecting a ton of data and many calculations. "Mathematically, time is not something you can average," he said. "If you open one message at 4 o'clock and then open another at 6 o'clock, the program might choose to say the correct time is 5 o'clock, but in fact you never open the email at 5 o'clock."

Depending on the email campaign, one metric that Encyclopaedia Britannica considers when determining successes is net revenue per 1,000 emails sent. It's the most objective metric when comparing campaigns and testing features such as the call to action button in the email.

Encyclopaedia Britannica also distributes two other newsletters. The daily, "On This Day," keeps people informed about special historic events that happened on that day. The monthly newsletter "Inside Britannica" highlights news topic such as the economy.

Aside from the Spend Time Optimization feature, Encyclopaedia Britannica will soon begin to test a feature Silverpop calls "Share to Social," which allows people to share emails on Facebook or Twitter. This will allow the encyclopedia company to track who has opened email and opted into the newsletter list from sharing the email. "We're trying to make it more viral," Adams said.