I've wanted to write some commentary on a few interesting issues that have come up recently in my work, so this will be the first in a series. Today's topic is email marketing and sanitizing your mailing lists.

When your website visitors sign up to receive email from you, the information that's collected from your website goes into a database. Unless you allow users to change their email preferences on your website, that database never gets updated.

Eventually, some of the email messages you send will be undeliverable, or "bounce" as it's called in the email marketing industry. Today I'll explore the two types of email bounces, some reasons for them and how to handle them.

So why do emails bounce?

Emails can bounce for a variety of reasons:

  • Maybe the email address is invalid, inactive or closed. The most common example here is when someone has moved on to another job and their old email address is invalid.
  • The recipient's mailbox is full.
  • The recipient's mail server is down at the time the message is sent.
  • The recipient's email system detects spam or offensive content.
  • The recipient has an autoresponse, like when they are on vacation.

The two types of email bounces are called "hard bounces" and "soft bounces." Seems simple enough, right? Not quite it's a bit more complex than that. Let's look at the two types and how to handle them.

Understanding "Hard Bounces"

Hard bounces happen when an email was sent to an email address that is no longer active. This could happen for a couple of reasons. One possible reason is that the recipient switched internet service providers and subsequently, their email address changes and their old email address is deleted.

Another reason a hard bounce can occur is because people change jobs, abandoning their old e-mail address. When someone leaves their job, places of employment terminate that person's email account. In my experience, 50% or more of your email marketing list could be comprised of work email accounts, so this is a common reason for hard bounces.

Tip For Reducing Hard Bounces

About the only thing you can do to combat hard bounces is to include a short paragraph on each of your e-mail communications letting customers know that if they change their email address they should let you know so you can update your contact list.

Understanding "Soft Bounces"

Soft bounces occur when email is sent to an active email address but the email is turned away before being delivered. Often, the problem is temporary -- the mail server might be down or the recipient's mailbox is full. The email might be held at the recipient's server and delivered later, or the sender's email program may attempt to deliver it again.

Soft bounces can also occur because a person has an out-of-office notification enabled on their work email account. 90% of the replies to email campaigns that we help deploy are out-of-office notifications. As a marketer, you wouldn't want to remove these people from your e-mail lists since they will eventually read the message and have the ability to receive future messages.

One note of caution about soft bounces: soft bounce reports from your email vendor are not always accurate because they often don't report all soft bounces or the actual reason for the bounce. When comparing email vendors, you should ask to see a sample bounce report so you can see what data is offered. If the vendor can't produce a sample report, inquire about how they handle soft bounces.

Save Money By Sanitizing Your Email List

What should you do with hard and soft email bounces?

Sanitizing your email marketing list is a very important component of running an email marketing campaign because it can save you money. Most email vendors charge you per email address you send to, and sending emails to invalid addresses is wasteful spending.

The first tip is simple -- you should remove hard bounces immediately after every campaign. Some email vendors will do this for you automatically without your attention, while some others require you manually remove the names. It depends on how sophisticated your email marketing campaign is, but you should remove hard bounces every time you send an email newsletter.

Soft bounces are tricky. You should monitor soft bounces, and if your email vendor allows you to read the messages that come back, you can monitor reasons for soft bounces. Typically, we do not remove soft bounces from my email marketing lists unless we notice that a particular address bounces several times over the course of a few months.

Most of the campaigns you deploy are relatively small in nature (under 25,000 names) so be sure to monitor your auto-replies and bounces manually. Using this method, you can find out why messages are bouncing back.

For more information, please see an article we wrote on cleansing MailChimp email lists. Even though it's written for MailChimp users, you can likely glean some valuable insights into cleansing your email lists.


While this one goes without saying, you should remove all people who unsubscribe from your mailings immediately after the campaign is sent. If you don't remove the person, you're breaking the law (CAN-SPAM). Most email vendors automatically unsubscribe email addresses for you, but if you're running your own campaign, you may need to do this manually.

Email marketing can be a very profitable tool in your marketing arsenal. Make sure you keep your mailing lists clean, and you'll save money and improve your open rates.

Cleansing your email lists is part of being a responsible marketer. You might also want to read "10 Rules for Being an Exceptionally Good Email Marketer" to get more insightful email marketing tips.

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