How Inactive Addresses Hurt Deliverability plus 3 Tips on What to Do

Posted by Tom Sather on

This article was originally featured on Deliverability.com

Inactive subscribers are a liability to anyone who sends email.  They hurt deliverability, which in turn reduces your response rates, and before you know it, your email program isn’t making as money as it used to.  Marketing managers usually understand that the key is to get rid of the dead-weight to solve these problems, but most executives try to solve the revenue problem through a numbers game and sending to even more email addresses, many of which are inactive as well.  So why should you care about removing inactive addresses?

ISPs define active vs. inactive addresses in a variety of ways through things like last log in date, how long they spend in their email client, and if the behaviors resemble that of a real person, such as reading, deleting and even marking email as spam or not spam, as well as other actions that we generally call engagement-level filtering.  Marketers look at it slightly different based on the data at their disposal, such as opens, clicks, conversions, or website activity.  ISPs care about active users because spammers have always been looking for ways to game the system, and one successful way has been to load their lists with inactive email addresses, because inactives will never hit the spam button, and complaints stay artificially low.  ISP postmasters are a smart lot though and caught on, and as a result, ISPs calculate complaints based on active and trusted subscribers.  This means that complaint rates are much higher for not only spammers, but any other sender as well.

So what does that mean for marketers?  Most marketers have been calculating complaint rates incorrectly for years by doing it off of total volume, rather than email delivered to the inbox.  If you’re mailing to a million addresses, and only half reach the inbox and 5,000 subscribers complain, then you have a 1% complaint rate, instead of 0.5% complaint rate based on total volume.  Let’s say you only have 250,000 of those subscribers active according to the ISP.  You now have a 2% complaint rate which is high enough to get you delivered to the spam folder, or maybe even blocked, at Hotmail, Yahoo, Gmail and AOL.

Let’s say you turn a blind eye to those inactive addresses.  Given enough time, they’ll turn into unknown users and spam traps.  Again, spammers ruin the email party through shady list practices that have high unknown users and spam traps.  ISPs respond by blocking and sending email to the spam folder when unknown users start to exceed 5% since that is a common link with spammers.  Additionally, ISPs recycle abandoned email addresses into spam traps because spammers buy and steal lists and this method is an easy way to find out who’s doing it.  Unfortunately for marketers, this means that mailing addresses that haven’t been mailed in awhile could result in spam traps.  Just one spam trap hit can cause deliverability issues, which is also supported by research we’ve done at Return Path.

There are other costs associated with delivering to inactives as well.  If you have a large list, mailing to inactives can put strain on your mail system and cause a lag in your delivery.  This can be a problem for time sensitive emails and during times, like Christmas, when the ISPs are under strain and trying to cope the increase in volume from all senders.  If you’re using an ESP, you’re also unnecessarily paying for emails sent to inactives who will never read your email in the first place.  By sun setting these addresses, you can deliver your mail on time and even save money.

Here are three simple things you need to do to sun set inactives:

  1. Define Active vs. Inactive based on your own business drivers.  Common methods may be through opens, clicks, purchases, conversions, or website activity.  You can also use a third party service like Connection Engine to help determine who on your file is an active email user.
  2. Once inactives are defined, create a strategy to encourage your subscribers to engage with your emails.  Some marketers send surveys, discounts, preference center updates, or other incentives to drive subscribers to open and click through on your emails.
  3. For those that did not engage with your win-back campaign, send a re-permissioning campaign and remove those that didn’t respond.

Any executive will have a hard time arguing against this given the benefits of higher inbox placement rate, cost savings, and an increase in response rates and revenue


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About Tom Sather

Email data and deliverability expert Tom Sather has worked with top-tier brands to diagnose and solve inbox placement and sender reputation issues as a strategic consultant with Return Path. As the company’s senior director of research, Tom is a frequent speaker and writer on email marketing trends and technology. His most recent analysis of new inbox applications’ effects on consumer behavior was widely cited across leading business media outlets including the Financial Times, Ad Age, and Media Post.

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