When you sent an email, did you ever receive an automatic message stating that it bounced back? If so, you’re not the only one—almost everyone has gone through this. Email marketers really deal with this on a regular basis.

But why does this happen? what are the typical causes of it? When a lot of emails are returning errors, what steps may be taken?

Let’s take a deep dive into email bounces and address each of these queries.

A brief definition

A bounce occurs when an email cannot be delivered. Typically, the email server will inform you of the reason.

Bounces can happen for numerous reasons. The simplest approach to understanding and dealing with them is first to categorize them.

There are two types of bounces: hard bounces and soft bounces.

  • Soft bounce – temporary glitches obstructing delivery.
  • Hard bounce – permanent failure in delivering an email.

Hard Bounce

A hard bounce means there is a persistent barrier preventing the delivery of an email. Usually, bounced email addresses are automatically and instantly removed from your list. All emails for upcoming campaigns will not include the cleaned addresses. Some of the most common causes of hard bounces in emails include:

  • The recipient’s email address entered is not valid.
  • The recipient’s email server has completely stopped delivery.

Soft Bounce

When a soft bounce occurs, the email address is legitimate, and the message was delivered correctly to the inbox. However, the bounce may have occurred for one of the following reasons:

  • The recipient’s mailbox is full.
  • The mailbox is not in use.
  • The recipient’s email server is offline or unavailable.
  • The message content has been censored.
  • The message is too long.

This is usually considered a short-term issue as the server can be patched, the recipient can clear their inbox, and the message size can be reduced.

Am I doing something wrong?

Don’t take it personally, we’ve all been through it.

Usually, when an email bounces, it sends a negative signal to the email sender’s server, potentially affecting the sender’s reputation and overall deliverability in the future. Additionally, they can negatively impact the recipient’s engagement metrics, such as click-through and open rates, leading to a decrease in email effectiveness.

However, knowing what causes an email to bounce can help reduce errors and improve deliverability. Just to list a few:

High Complaint Rate

A high complaint rate is one of the main reasons why your email will end up in the spam/junk folder or get your IP blacklisted. Complaints are recorded when a user marks your email message as spam (by clicking the “Report as Spam” button).

Each ISP has a threshold for spam complaints, and if your email campaign crosses that line, your messages will never reach your user. This is because ISPs are strict about their customers receiving only wanted email.

Spam Filters

Spam filters can be a problem as they label valid emails as spam, causing them to be forwarded to unintended recipients. This problem often occurs when emails contain specific keywords or suspicious attachments, or when the sender’s IP address or domain has a poor sender reputation.

In some cases, spam filters can be blamed for the increased undelivered communications. None of your mass-sent messages are likely to reach the intended recipients and be received if you happen to use an email address or IP address that is blacklisted.

If you want to know more about spam traps and anti-spam strategies, take a look at this blog from Valid Email, they’ve taken a deep look at it.

Permission-Related Issues

Your email list is where a good (or poor) email distribution always begins. A good list is created with strict permission requirements. Building an engaged audience can largely be done through a solid opt-in strategy.

However, just because permission was given once doesn’t mean it will always be granted. You’ll have to account for list fatigue and low response rates resulting from changing user needs over time.

You need your users to frequently open and click on your emails because ISPs now pay special attention to engagement rates. To maintain high email delivery rates, consider the following tips and best practices:

  • Ask for permission to keep sending emails to non-responders and systematically remove them.
  • Regularly request users to update their preferences in the preference center.
  • Make sure the unsubscribe option is functional and obvious.

In the end, users should deliberately unsubscribe from your list rather than mark you as spam. The latter causes problems for your email application by raising red flags with ISPs.

How to improve your bounce rate

The success of any email marketing strategy hinges on properly functioning email infrastructure. This is why it’s important to have a solution to monitor and reduce bounce rates.

The best way to reduce the number of bounces is by following some key email deliverability best practices. This includes the following:

  • Maintain good list hygiene: Purge your list regularly of invalid emails and non-responders. High bounce rates can affect your sender reputation so keeping your lists clean will go a long way to achieving higher email delivery rates. In the SendGrid platform, you can review and manage your bounce lists right from your dashboard. Here, you can purge blocks or hard bounces after a certain number of days and specify whether or not you want these bounce messages forwarded via email.
  • Use double opt-in: Send a confirmation email when users subscribe to your list. This way you can ensure that the user’s email is not only valid, but that they in fact want to receive your email messages.
  • Monitor your email delivery: Track your email delivery rates by paying close attention to your bounce rates as well as your response rates. With regular monitoring, you can catch potential failures before they happen or before they do too much damage.