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The Ultimate Guide to Email Bouncing: Types, Causes, and Fixes

  • Yurii Shumak
  • 6 min read
The Ultimate Guide to Email Bouncing: Types, Causes, and Fixes


Have you ever emailed someone and it bounced back to you? That's what we call email bouncing! It can be a real headache, especially for marketers, advertisers, and business owners who rely on email to connect with their customers and prospects.

Email bouncing can have a significant impact on the success of your email campaigns, which is why it's crucial to understand the ins and outs of it. In this article, we'll walk you through everything you need to know about email bouncing, from its types and causes to practical tips on how to minimize its impact on your customer interactions. So, sit back, relax, and let's dive into the world of email bouncing!

What is Email Bouncing?

When you send an email, sometimes it doesn't make it to the intended recipient's inbox, which is called an email bounce. You'll usually get an automatic message explaining why it didn't go through. There are two kinds of bounces: hard and soft. Email bouncing can cause frustration for both the sender and recipient, but understanding the reasons behind it and how to address it can lead to better email deliverability and engagement.

Types of email bounce – Hard bounce and Soft bounce

To ensure the success of your email marketing efforts, it is important to keep track of your email bounce rate. Bounces can occur for a variety of reasons and are categorized as either soft or hard bounces. Understanding the distinction between these two types of email bounces is key to optimizing your email marketing list.

Hard bounce

When an email fails to reach its intended recipient for permanent reasons, it is referred to as a hard bounce. Such a failure commonly occurs when the recipient's email address is either invalid or no longer in use.

This could be due to a typo by the subscriber, or the domain name might have ceased to exist. Hard bounces can be troublesome since they negatively impact the rate at which your emails are delivered and your reputation as a sender.

Soft bounce

When an email fails to deliver due to a temporary issue, it's known as a soft bounce. This can be because the recipient's email inbox is full or there is a problem with the receiving server. However, don't worry, as soft bounces can be retried a few times.

If the email still doesn't go through, it's time to take action and remove that subscriber from your list, as it is now considered a hard bounce.

Reasons for Email Bouncing

For instance, when your first sending sales email message fails to reach its intended recipient, it is known as an email bounce. This can happen due to various reasons such as a non-existent email address, a full inbox, server outages, poor sender reputation, flagged content, or restrictive DMARC records. There can be more reasons than those listed above. Some of these reasons can be temporary, while others are permanent.

To troubleshoot email bouncebacks, you must first understand the type of bounce category your email falls under.

There are three types of bounce backs — soft bounce emails, hard bounce emails, and blocklisted emails — that can disrupt the delivery of your email.

Hard bounce emails

When an email is permanently undeliverable to a specific email address, it is known as a hard bounce.

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There can be various reasons for the occurrence of a hard bounce email:

  • Fake Email Address: Some people give fake email addresses, especially when asked for an address in exchange for something online, like content or a discount. Using double opt-in can help avoid these bounces.
  • Incorrect Email Address: There's no spell check in email address fields, so typos happen, leading to incorrect email addresses.
  • Email Blocked: Some sender domains, like governmental or institutional, have stricter spam filter settings, and some recipients may have purposely blocked your email address. If it's due to spam filter settings, ask them to add you to their contacts.

When it comes to hard-bounce emails, there's no easy fix. However, it's important to take action by removing any hard-bounced email addresses from your mailing list. If you let them accumulate, your emails could end up being blocklisted. So, it's best to stay on top of things and keep your list up-to-date.

Soft bounce emails

When an email server temporarily rejects an email, it's called a soft bounce. However, this is just a temporary problem, and email services usually attempt to resend messages that have soft bounced.

There are various reasons why an email might soft bounce, such as:

  • Mailbox full: When a recipient's mailbox reaches its storage capacity and has no more space to receive new emails, your email will bounce back to you.
  • Email size: If the size of your email exceeds the limit set by the recipient's email client or server, your email will be bounced back. This can happen if you include large attachments or heavy images in your email.
  • The server is down: If the recipient's email server is down, it may have crashed, been overloaded, or been undergoing maintenance. In this case, you will need to wait to send the email again to the recipient's address.
  • Autoreply: When someone sets up an auto-reply, it means that they are out of the office, on vacation, or otherwise unable to respond to your email immediately. Your email may bounce back with an auto-reply message.

Blocklisted emails

Email service providers (ESPs) create blocklists to sift through harmful or exploitative content, such as spam and malware, and eliminate them. These blocklists are not meant to complicate the process of sending emails, but rather to safeguard the recipients of the staggering 300 billion emails that are sent every day.

  • Spam complaints: Complaints from recipients can send your emails to spam folders/blocklists
  • High bounce rates: Poor email list hygiene can lead to high bounce rates
  • Surge in list size/volume: Rapid growth of email list or sending massive amounts of email can signal spam or a bought list
  • Bad content: Use of spammy words in the subject line or content can trigger filters

The Impact of Email Bouncing on Email Deliverability

When you send out a batch of emails, it’s important to keep an eye on the bounce rate. A bounce rate of 2% is normal and nothing to worry about, but anything over 5% is cause for concern. This is because a high bounce rate can negatively impact your email deliverability, which can ultimately hurt your engagement rates and sales.

Email providers view a high bounce rate as a red flag for poor email marketing tactics or low-quality content, which can lead to your emails being marked as spam. This is why it’s significant to take steps to reduce your bounce rate and maintain a positive digital reputation.

Remember, every bounced email is a lost opportunity for customer interactions, so it’s worth the effort to keep your bounce rate as low as possible.

How to Detect Email Bouncing Using a Bounce Email Checker

It's not a big deal if you receive a couple of bounced emails occasionally. However, leaving the issue of bounced emails unattended can be troublesome. To prevent the negative impact of an unclean mailing list, it's advisable to utilize a reliable bounce email checker tool.

We have a few that which you can pay attention to:

Mailfloss is a great tool that many professionals use to verify large mailing lists in bulk. It's an automated email bounce-back checker, which means you won't have to worry about managing the process. If you want to try it out, you can get a 7-day free trial.

EmailListVerify is a highly-rated tool that checks for syntax errors, inactive or non-existent domains, and spam traps that can hinder your emails from getting delivered. It is trusted by big players in the email marketing industry, such as Mailchimp and Shopify. With EmailListVerify, you can verify up to 1,000 addresses for free.

Clearout is a tool that does exactly what its name suggests — it gets rid of bad email addresses using different methods. It can detect emails that come from blacklisted domains, spam traps, and those that have previously caused hard bounces. You can try Clearout for free with up to 500 addresses.

Tips for Fixing Email Bouncing – Hard Bounce and Soft Bounce

You have a few different strategies at your disposal for reducing your bounce rates.

Tips for Fixing Hard Bounces:

  • Double-check the email address: Mistakes happen, and sometimes a hard bounce occurs simply because the email address was spelled incorrectly. Make sure you've got the correct email address and try sending the email again.
  • Remove invalid email addresses: If the email address is no longer active or invalid, it's best to remove it from your email list. This will help avoid future hard bounces.
  • Use a free email validation service: If you're unsure about the validity of an email address, there are free services available that can help you verify it and prevent hard bounces.

Tips for Fixing Soft Bounces:

  • Wait and try again: Soft bounces are usually temporary and often caused by factors like a full mailbox or server downtime. Wait a bit and then try sending the email again.
  • Check your email size: If your email includes large attachments or images, it may be too big for the recipient's mailbox. Try sending a smaller email or sending the attachment through a different method.
  • Watch your email-sending habits: Sending too many emails too quickly can trigger spam filters or cause temporary server issues. Pace yourself and keep an eye on your email metrics to avoid future soft bounces.

Sum up

It's important to understand and address email bouncing to ensure your emails are being delivered to the right people and avoid the spam folder. By following our tips, you can minimize email bouncing and improve your email deliverability and engagement. Keep these tips in mind to help you build stronger relationships with your customers and prospects through email!

Yurii Shumak

Yurii Shumak

Technical Content Writer, Mailtrap

I'm a technical content writer and Mailtrap contributor passionate about helping companies and products bridge the gap between people, processes, and technology. In other words: the trenches are where I spend most of my time.

Link: Mailtrap

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