What is the ideal list size for an e-mail send?

Published on .

Most Popular

Answer: The ideal list size for an e-mail send is one person. Obviously, as marketers, we want to grow our e-mail subscriber database, but we should not send undifferentiated broadcast e-mails to our entire database.

In a recent study by ExactTarget, list size was an incredibly strong predictor of both open and click-through response rates. Open and click-through rates were approximately 2.5 times higher for e-mails sent to fewer than 100 subscribers than for e-mails sent to 100,000 subscribers or more, indicating that smaller is better when it comes to targeting our messages.

There are two scenarios to consider:

  • Subscriber-initiated e-mails: e-mails triggered based on the subscriber doing something and initiating contact.
  • Sender-initiated e-mails: e-mails sent based on the sender’s desire to leverage the subscriber database to initiate contact.

For subscriber-initiated e-mails, the subscriber has begun the dialogue through an event such as registration, cart abandonment, site search or a telephone call. These e-mails respond to subscribers showing interest through their behavior. This is the best time to send a highly personalized message. Studies consistently show significantly higher response and conversion rates for these communications.

The challenge is anticipating the appropriate response and setting up the processes to react to these events. Outline the scenarios, create the content ahead of time and program the triggers to deliver the response message with appropriate personalization strings and dynamic content. For example, look at people who have searched for a product on your site and follow up with a limited-time offer for items in that product category.

For sender-initiated e-mails, the single best way to boost e-mail response is to segment your audience into smaller lists. The smaller the audience, the better you can target messages to your subscribers and make your e-mail communications relevant. Before sending, consider the following in order to increase response:

  1. Which subscribers should receive this message? Identify at least one group that should not receive the message. If you can’t, you probably aren’t protecting your subscribers from irrelevant messages. This will eventually erode your credibility and accelerate list fatigue. For example, don’t send in-store promotions to people who don’t live near a store. Don’t send service offers to people who have already signed up for the service. Stop sending newsletters to people who only open promotions.
  1. What information can we leverage to increase the relevance of this message? If you have collected information on subscriber interests, make sure this is leveraged to drive dynamic content. Use demographic data to determine the right products, message and offers to deliver. Use past response data to determine the types of information that interest the subscriber.

A successful marketing program is not rooted in campaign-level response but in long-term customer value. It is nearly impossible to convey a single message that is universally relevant to your customer base. Segment your audience into the smallest groups possible and leverage the data you have to drive relevant content.

Morgan Stewart is director, strategic services for e-mail service provider ExactTarget (

In this article: