What makes an email bounce? What marketers need to know

You put your heart and soul into email campaigns for your clients. You spend hours selecting just the right graphics, writing relevant copy, and segmenting your audience so your content goes to just the right inboxes. That’s why it hurts to see an email bounce.

Although this might frustrate the perfectionist inside you, bounces are completely normal in email marketing. You can’t avoid them entirely, but you can maintain a healthy email bounce rate.

Certain factors you can control, but others you’ll have to leave up to the email powers that be and adjust your tactics accordingly.

This blog will go over what makes emails bounce and how to keep your bounce rate low.

What does an email bounce mean?

Email bounces are like the “return to sender” of the email marketing world. They mean that your email service provider could not deliver the email you sent for any number of reasons.

According to Better Bounces, 31 billion emails bounce every day, which means it happens to virtually all businesses. In a majority of cases, the “it’s not you, it’s me” line totally applies: Something went wrong on your subscriber’s end that resulted in your email not making it into the inbox.

But it’s hard not to have the nagging suspicion that if you’d only done something differently, you would have gotten different results.

Why do emails bounce?

  1. The recipient’s mailbox is full

  2. Your IP address is bad

  3. The subscriber blocked you

  4. The recipient has an out-of-office reply set up

  5. The server is overloaded

  6. The receiving server doesn’t trust your content

  7. The subscriber’s email address is invalid


Let’s take an in-depth look at these reasons.

  • The recipient’s mailbox is full. Most email providers only allow so much storage. If your subscriber has reached their limit, they can’t receive emails from you or anyone else.

  • Your IP address has a bad rap. Using a bad email service provider can result in your messages not being delivered. If another marketer is sending spam from the same IP address, for example, this damages the IP’s reputation.

  • The subscriber blocked you. Instead of clicking “unsubscribe,” the recipient could have simply blocked your email address from sending emails. Ouch.

  • The recipient has an out-of-office reply set up. Auto-responders can trigger a soft bounce until the recipient turns off this notification.

  • The server is overloaded. Servers get tired, too. Maybe it just needed a break.

  • The receiving server doesn’t like your email’s content. You can control several factors that might be giving you that dreaded “email bounce” notification. (We’ll go over these below.)

The subscriber’s email address is invalid. Maybe they entered it wrong upon signup, or maybe they may have given a fake address. It hurts but it happens and this triggers a bounce email address.

How to interpret each bounce from email address to email address

What does an email bounce mean for marketers? Let’s take a look at the different types of bounces and steps you can take to minimize the damage.

What is a soft bounce?

You shouldn’t worry too much about a few soft bounces—these are totally normal and often part of a healthy email bounce rate. A soft bounce generally means that something went wrong with the subscriber’s email server, due to any of the reasons outlined above. Luckily, you’re probably not separated from this user indefinitely.

Soft bounces are temporary.

In this case, your email server will generally attempt to resend the email several times over the course of hours or days until it manages a successful delivery. Most email service providers have a standard period for re-attempting to deliver soft bounces. If your server still can’t deliver the email after this period, it gives up.

Depending on your email service provider, the failed soft bounce might change to a hard bounce after exhausting all attempts.

What is a hard bounce?

Marketers shouldn’t take hard bounces lightly. If you see a hard bounce from an email address, immediately remove that recipient from your subscriber list.

Think of it as being blocked. You absolutely cannot contact them and, for your own good, you shouldn’t continue to try.

Hard bounces are permanent.

Hard bounces indicate the email simply isn’t valid. The subscriber could have typed it wrong or simply changed their address and deleted the old one. Either way, remove the subscriber and continue sending to your remaining list.

You might feel tempted to correct their typo and enter what looks like the “real” email address. This is a bad idea. New General Data Protection Regulations (GDPR) require subscribers to opt-in for email communication from marketers. When in doubt, just stay out of the legal gray zone.

What can marketers do to lower their email bounce rate?

For a healthy email bounce rate, shoot for 2-3% depending on the size of your list. Still, remove those hard bounces ASAP.

When it comes to soft bounces, however, you can take a few steps to ensure that you’re optimizing your email deliveries.

Use a reputable email service provider

A solid ESP, with a full M³AAWG membership, will have a dedicated compliance and deliverability team that proactively monitors IP health and works with clients to maintain a great sender reputation. This drastically reduces the risk for all customers by having a robust permission-only sending policy and adhering to the leading email marketing industry standards.

Verify your domain

This is easy to do through your email service provider and can lower your bounce rate. It basically means you’ve given a specific server permission to send emails from your domain addressed as your website.

Keep your images (and emails) small

Email clients may simply send large emails straight back to the sender. If you’re getting a lot of bounces, check the size of your emails. Here are some common limits:

  • Gmail: 25Mb

  • Outlook: 20Mb

  • Yahoo: 25Mb

It’s generally a good idea to aim small in the first place because this will help your emails load quickly on mobile devices.

This email from Whole Foods contains relatively small graphics along with a good balance of actual copy to ensure optimal deliverability.

Whole Foods balance of graphics and copy

Image Source: Really Good Emails

Avoid triggering spam filters

Spam filters update their algorithms all the time. It’s important for marketers to stay updated on what constitutes spam so they can avoid getting flagged and damaging the reputation of their brands or ESPs.

In general, it’s a good idea to limit the size of your emails and graphics, avoid trigger words like “money,” avoid writing in all caps. Don’t send email campaigns with attachments or lots of exclamation points either—they could look spammy to readers and affect engagement. And low engagement really can cause your emails to be filtered as spam.

This email from Blue Apron uses a good balance of images, copy, and links. It also provides an unsubscribe link at the bottom of the email to stay in compliance with international anti-spam laws.

Blue Apron balance of graphics and copy

Image Source: Campaign Monitor

Use a solid signup form and double opt-in features

It’s easy to avoid hard bounces if you take advantage of double opt-in features when your subscribers sign up. After entering their email address for the first time, each subscriber will receive an email that asks them to verify their place on your list.

Each subscriber physically has to click “yes” or follow a specific link to sign up. This gets rid of invalid emails right away.

Opt-in emails like this one from Auto Trader are a perfect solution for removing hard bounces before they happen. Plus, they ensure that only people who really want to hear from you get your emails.

AutoTrader opt-in email example

Image Source: Really Good Emails

Use an email bounce checker

Better Bounces provides a free email bounce checker to help marketers understand error codes and what went wrong so they can do better. Your email service provider should also help you with special tools and information about maintaining a healthy email bounce rate.

Clean up your subscriber list

Continuing to send emails to invalid addresses of hard bounces can damage the reputation of your IP address and snowball into even more bounces. Keep your subscriber list clean by removing hard bounces as soon as possible. This will also ensure that only subscribers who actually want to hear from you are receiving your emails.

Wrap up

Why would a valid email bounce? Email bounces are a normal part of email marketing. If you’re getting a lot of soft bounces, adjust your campaigns and try again. Hard bounces, however, should be removed immediately, or you could risk damaging the reputation of your service provider. In general, shoot for a healthy email bounce rate and keep sending relevant content to your subscribers.

Are you interested in sending emails from a high-quality IP address with customizable mobile-friendly templates? Find out how Emma can help.

About the Author

Lane Harbin is a senior content marketing manager at Emma. When she’s not geeking out over email marketing, she enjoys binge-listening to podcasts, catching up on the latest tech news, and constantly rearranging her living room.

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