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Email bounce management is a topic in email marketing that can sometimes be overlooked by some senders. As a sender, you should know that email bounces (i.e. delivery errors) can be managed through your ESP, but don’t forget to define a procedure in your company on how to properly handle email bounces. This brings us to two basic questions: “why should I manage email bounces?” and “who would do this in my company?”

Email bounce management

Why and who should manage email bounces?

Let’s answer the first question with another question. Why should you keep sending your emails to an inbox that no longer exists? Depending on the type and number of bounces, inbox providers (ISPs), such as Gmail, monitor email bounces and can lower your deliverability rate. ISPs can even block altogether your emails from reaching your subscribers’ inbox. It’s no surprise that inbox engagement is an important metric for ISPs. This is one of the reasons why most high volume senders have bounce management tactics in place and communicate on a regular basis with the ESP staff.

When your email campaign shows a high number of email bounces and incorrect/invalid email addresses, ISPs see this as a potential warning sign and it’s one of the many parameters ISPs use to establish your sender reputation. A high number of bounces can also be an indication that you may have collected (or purchased) email addresses without following email marketing opt-in best practices.

As you can see, bounces affect marketers, ESPs, and ISPs in different ways. Each one can and does manage email bounces! This explains the “who” from the above questions. Let’s see how:

  • Marketers manage bounces to be able to reach all of their mailing list contacts.
  • Email service providers (ESPs) send millions of emails each month and keeping deliverability rates high is important. ESPs try to be conservative, as even a small error can have a big impact on all of their customers’ emailing.
  • Internet service providers (ISPs) use email bounces stats to establish the quality of incoming emails from senders. ISPs also have the choice to allow or reject your email into their inboxes. If you’re interested, the IETF has a few technical guidelines.

When do email bounces occur?

Another question senders may have is at “what time do bounces occur?” The answer depends on the type of bounce. Some bounces happen right away at the time of send, at different intermediate stages, or at a later stage, such as with an asynchronous bounce. ESPs are notified of bounces and try to collect all the bounce information, such as the parsing of the email message and the bounce error code.

This bounce information is however not too intuitive for marketers, which leads to some confusion and ambiguity on what to do. A good article on this issue is from Port25 in which they propose a new bounce code system.

What is proper bounce handling?

During the early days of the internet at the Email Deliverability Summit in 2000, both ISPs and ESPs came together and defined when one should remove an email address from a mailing list:

  1. Three (3) consecutive delivery rejections have occurred; AND
  2. The time between the most recent consecutive delivery rejection and the initial consecutive delivery rejection is greater than fifteen (15) days.

For more information, view the ISIPP email policy standards.

To date, this rule remains a good starting point on how to assess when to remove email addresses from a mailing list. More recently, the Messaging, Malware and Mobile Anti-Abuse Working Group (M3AAWG) reaffirms the importance of proper bounce management in version 3.0 of their Best Practices for Senders publication.

How does MailUp handle bounces?

Over the years, the deliverability team at MailUp has always kept an eye on bounce management, letting customers know of the best email marketing tactics for handling bounces and more generally on how to grow their mailing list following email marketing best practices, including double opt-in subscription to limit incorrect or invalid email addresses being added to their mailing lists.

And that’s not all. Behind the scenes, the MailUp platform has in place a number of sophisticated automated algorithms and systems that are the basis for our vetting process. These systems allow us to monitor the millions of emails that our customers send every month through our sending infrastructure. For example, we monitor the number of hard bounces from our senders, segmented by industry and historical data, which in turn can be used to provide advice if a particular email campaign has gotten higher than expected bounces to our senders. In addition, if a certain email campaign gets a high number of spam complaints, our automated systems may see this as spam and to prevent further deliverability issues by temporarily suspending a MailUp account.

The deliverability team is very transparent with MailUp customers and our developers are constantly introducing new features to the MailUp platform to better manage bounces and unsubscribes. A recent example is with the special unsubscribe feature, which adds bounced email addresses into a special status after a given number of consecutive bounces have occurred.

Depending on the type of bounces and the time interval, these bounced email addresses can either be put back into your mailing list (such as after a mailbox full bounce) or unsubscribed from your mailing list. In detail this depends on:

  • The type of bounce. A hard bounce or a DNS error soft bounce is very different from a temporary soft bounce and a mailbox full bounce.
  • The opt-in method. A confirmed opt-in is a much more reliable method from a single opt-in method or a bulk import. It’s far less likely that confirmed opt-in subscribers will bounce. Read more on the confirmed opt-in method.
  • The level of subscriber engagement. Active subscribers who have opened and clicked on emails in the past is a good indication of their engagement. It is far less likely that recent, active subscribers will bounce as opposed to inactive subscribers that you don’t have any past open or click data on.

These three parameters are to be viewed as a guideline when making a decision on unsubscribing or not bounced email addresses. There isn’t necessarily a one fits all approach and you should use your best judgement when managing bounces, especially with hard versus soft bounces.

A few practical tips: Keeping your mailing list up-to-date

The first tip is to use a confirmed opt-in method to collect email addresses on your website and other web & social properties. But don’t stop here, be sure to email your subscribers once in a while. Don’t let your mailing list turn inactive.

If your mailing list is more than a couple of months old and you haven’t sent an email since, setting up a re-engagement campaign can be a good approach. Why? Because some of those email addresses may be no longer in use, hence the likelihood of a high number of bounces, which we want to avoid!

A simple re-engagement campaign should clearly state and establish:

  • Who the sender is. Let your subscribers know it’s your company.
  • State why you’re contacting your subscribers and how you collected their email address.
  • Emphasize your value proposition and why your email is relevant to your subscribers.

For ideas view these examples of re-engagement campaigns and learn how to setup a re-engagement campaign in MailUp in this help article.

How do I optimize an old, inactive mailing list?

If however your mailing list does become out-of-date due to months of inactivity, the chances of bounces and spam complaints increase. When this is the case, we strongly recommend to clean your mailing list before sending an email campaign via MailUp. With old, inactive lists even a re-engagement campaign can cause a high number of bounces and spam complaints that can trigger a temporary block or permanent suspension of your MailUp account. This is one of the reasons why you should not use MailUp as a list cleaning tool, but rather use a list cleaning service.

There are a number of list cleaning services that can effectively remove bounced email address (such as email addresses that have been disabled) and, therefore, avoid a high email bounce rate, which is a red flag to both ISPs and ESPs. The rule of thumb is to clean your mailing list first to avoid any deliverability issues and then re-engage your subscribers.

Always keep in mind that having the permission (i.e. opt-in) from your subscribers is one of the most important aspects of email marketing today, and that all else lies on their consensus. A best practice in using a list cleaning service is to re-confirm the opt-in status of your subscribers. This confirmation from the list cleaning tool yields great results when importing your clean, opted-in mailing list back into your MailUp list.

If you’re looking for a list cleaning service that is integrated with MailUp, check out Datavalidation on

How do you manage email bounces?

Did you find this blog post useful? Let us know in the comments below! And, let us know how you manage email bounces.

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