Email Deliverability

SOS! My Emails Are Bouncing!

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Email bounces are among the most dreaded outcomes for email marketers—especially when they’ve previously enjoyed normal delivery rates.  

After all, a bounce means subscribers will never get to see the snappy campaigns that take time and effort to create. Plus, any potential revenue those emails might have earned is gone in an instant.

To keep your bounce rates healthy, let’s take a look at the different types of email bounces, why they happen, and how to remedy these issues before they create larger problems for your email program.

Put on your email detective hat

When senders start seeing their bounce rates creep up, it’s time to go into detective mode to figure out what the catalyst was so they can make an action plan to resolve the issue.  

Luckily, all email detectives start the investigation armed with one important clue: When an email bounces, a bounce error code will be sent from the recipient’s mail server, which you can use to diagnose the cause.  

Sometimes the answer isn’t cut and dried. There are many reasons why an email might have bounced. But these handy codes can tell you if there’s an issue with your list, indicate if you’re on a blocklist, or alert you if there’s a problem at the mail server you’re trying to reach.   

Common bounce codes include the following:  

  • 2.2 Mailbox is full
    • Senders aren’t to blame here. This code indicates a problem on the recipient’s end. It means the recipient’s mailbox is full, which causes emails to bounce until space becomes available. 
  • 1.8 Bad sender’s system address
    • This code means that the mailbox provider you’re trying to send to has placed you on a blocklist, likely for sending too much of what they consider spam. When this is the case, senders might see a sudden influx of this code from recipients with the same mailbox provider.

Bounce rates should be one of your regularly monitored email performance metrics so any deviations from the norm become apparent sooner rather than later. Continuous monitoring is important to understand the trends within your own email program and see how you’re doing compared to industry benchmarks. 

It’s rare to see a zero percent bounce rate, so don’t go into a panic if you’re seeing 0.2 percent. But if you see bounce rates suddenly increasing from your usual percentage, it’s time to start looking into damage control.

Generally speaking, a bounce rate over two percent is worth keeping an eye on.

What’s the big deal about bounce rates? 

Given all the email metrics marketers need to track, are bounce rates really worth your attention? In short, yes.

High bounce rates can have a negative effect on your all-important sender reputation. They can be a negative signal to mailbox providers (MBPs) that you’re sending to an unhealthy list (i.e., one that isn’t cleaned and verified regularly) and that you’re failing to make sure your subscribers are actively engaged with your program. You can also see more bounces and more email go to spam if you’ve ended up on a blocklist, which is a huge no-no for maintaining a solid reputation.

Bounces can also have a significant impact on your ROI. Let’s do some quick math. For an email program that sees an average revenue of $0.5 per email and sends to an audience of 300,000, hitting a bounce rate of six percent could result in a loss of over a million dollars per year, assuming they send 10 campaigns per month.

As we can see, the losses add up quickly when a sender is having delivery issues,

To avoid this outcome, it’s important to understand the two major types of email bounces. 

Soft bounces 

Soft bounces are caused by a temporary delivery failure. Delivery is often attempted multiple times over a span of time or several tries. Common causes include:  

  • The recipient’s mailbox is full
  • The mail server is down 
  • Your email message is too large
  • The mail server has been sent too many messages within a certain period of time

There are other possible causes, but these are some of the more probable culprits.  

Sometimes, like when a soft bounce occurs due to a temporary server issue, there isn’t much senders can do. However, in the case of repeated soft bounces, it’s worth creating a plan with your ESP (Email Service Provider) to suppress these contacts after a certain number of soft bounce sends with no recent activity. 

Why? If your list has many users with full mailboxes, (which causes repeated soft bounces for extended periods of time) it’s likely that some of these addresses are no longer actively used. So, continuing to send to them will reflect negatively on your sender reputation 

Hard bounces 

Hard bounces are the result of a permanent delivery failure. There will be no repeated attempts to send these messages. Common explanations for this type of bounce include:  

  • The recipient address no longer exists
  • The recipient address is unknown

Seeing a lot of hard bounces lately? One common reason might be subscribers using work email addresses to subscribe to your email program.

If they leave their jobs, the address will usually be terminated. Given the volatility of the current job market, senders might be experiencing more hard bounces than usual as their contacts transition jobs.

Continuing to send to these hard bounce addresses is a major red flag to MBPs. Many ESPs have built in suppression triggers related to hard bounces, and it’s vital to check and make sure that this is configured for your program.

If it isn’t, you might have to work out a process or automated workflow using the hard bounce trigger to suppress these contacts.


Closely tied to bounce rates are email blocklists (also known as blacklists). A blocklist is a list of servers or domains that a blocklist operator has identified as sending spam. The best way to measure the impact of a specific blocklist on your program is to look at your bounce codes—if you have access to them. You can also try a free blocklist lookup tool

As mentioned previously, bounce codes will often point to a specific blocklist in the bounce reason.

Let’s say the news comes back and it isn’t good—you’re on a dreaded blocklist. Some blocklists will have mitigation steps instructing senders how to remove themselves. If that’s the case, there’s no time to waste!

But keep in mind that most blocklists are dynamic and will resolve over time when the problematic behavior stops.  

Your blocklist strategy may also depend on which type of list you’re on—domain-based or IP-based.

An IP-based blocklist looks at reputation based on a sender’s IP address. If you use a shared IP, you’ll have to talk with your ESP about any blocklist issues and see about getting placed into a shared pool of senders with better reputations.

When using a dedicated IP, resolving the issue is up to you.  

Domain-based blocklists look at a sender’s top-level and sub-domains when gauging reputation. These blocklists can have a larger impact on your delivery rates, since it’s common for a company to use multiple IPs to send from one domain.  

Following email marketing best practices, having suppression plans in place for both hard and soft bounces, and proactively monitoring your bounce rate metrics are just a few steps you can take to avoid ending up on a blocklist.


These are just a few ways to identify and fix bounce issues before they snowball into larger problems.

But there are other steps you can proactively take to improve your bounce rates, too.

Becoming a certified sender requires hitting certain best practice metrics and increases your reputation with 75+ global mailbox providers. Luxury gift provider Red Letter Days, for example, went through the certification process and saw a 75 percent reduction in their bounce rate.  

For example, cleaning your list with a validation tool like BriteVerify can help with the list hygiene aspect of your reputation and help identify unknown domains.

A straightforward way to avoid email bounces is to keep your list clean. To learn more about list hygiene, download our Guide “Clueing in on List Hygiene: Catch the Culprit of Poor Email Performance.”