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3 Metrics to Measure the Health of Your Email Subscriber List

Posted by Chris Winter on Dec 10, 2015 1:44:06 PM

Metrics to Measure the Health of Your Email Subscriber List

A healthy list is the key to a successful email marketing program. In 2015, ReturnPath reported that just 79% of commercial emails worldwide made it to the inbox. This means for every five emails sent, one never reaches the intended recipient. Instead, this email ends up in a spam folder or goes missing—most likely blocked by the mailbox provider. Poor list hygiene is likely to fault. Good deliverability requires constant vigilance and discipline.

For every five emails sent, one never reaches the intended recipient.

List Churn Metrics

Hard bounces, unsubscribes, and complaints all factor into what is known as list churn*. If these metrics get too high, they can negatively affect sender reputation, deliverability, and ultimately your ROI.

*List churn is the average percentage of email addresses that marketers can expect to lose in a given year. List churn typically ranges between 20-50% but can be reduced by practicing good list hygiene and adhering to industry best practices.

Here are the 3 Metrics to Measure the Health of Your Email Subscriber Base:

  1. Hard Bounces

What Are They?

A permanent reason why an email cannot be delivered to an email address. These records should be flagged and suppressed immediately.

Reasons for Hard Bounces:

  • The recipient’s email address does not exist
  • The domain name does not exist
  • The recipient’s email server has completely blocked delivery


Failure to remove hard bounces from future email campaigns can severely hurt sender reputation and your ability to get future emails delivered to the inbox.


  1. Unsubscribes

What Are They?

When users manually opt-out from receiving all future messaging from a specific brand or company.

Subscribers are most likely to unsubscribe when:

  • They receive impersonal and irrelevant email
  • They don’t recognize the sender
  • They receive more email than they expect or want


Unsubscribe rates are an important metric to pay attention to as it provides good insight into what type of content your subscribers value or, in this case, don’t value.


  1. Complaints

What Are They?

Feedback loops are tools made available to email marketers that enable subscribers to report spam.

By removing subscribers from a list who don’t want to receive emails, one can:

  • Reduce the complaint rate
  • Increase customer satisfaction
  • Reduce sender questions and end-user complaints


With lower complaint rates, ISPs are much more likely to allow your messages to reach the inboxes of those subscribers who actually want to receive them.


How to Improvie the Health of Your Email Subscriber List

You can build and maintain a strong sender reputation by developing an email program your subscribers care about. Monitor your reputation and engagement data (opens & clicks) to understand how mailbox providers view your campaigns. A high number of unsubscribe or spam complaints mean that you are jeopardizing the health of your email marketing list and your sender reputation; it may also mean that your content pieces or offers aren't relevant. By keeping a close eye on these metrics you will be able to immediately see downward trends and catch small issues before they turn into big problems.


Practicing Good List Hygiene

Many marketers view list hygiene as the removal of valuable subscribers from their sender list. While yes, you may be losing subscribers, you are in fact pruning the portion of your list that doesn’t add to your bottom line. If you’re worried about the optics of losing a large chunk of your subscriber list, check out our article about list growth ideas in order to gain healthier and more engaged subscribers.

Topics: Email Deliverability, Email Marketing Best Practices, Email Marketing, List Hygiene

The Inbox Marketer Blog

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