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9 Reasons Why Emails are Not Delivered

May 23, 2022
You might be completely at a loss the first time you see that an email has bounced or has not been delivered.
The truth is, when an email bounces, it might not always be the fault of the sender. Whether an email is a hard bounce or a soft bounce will help you determine what has gone wrong. And the first step in reducing the number of emails you send that do not get delivered is to understand what an email bounce is and some common reasons why they happen.

What is an Email Bounce?

An email bounce occurs when a marketing or commercial email is not delivered as intended. There are several different reasons why they may happen.

The most crucial thing to remember is that not only do email bounces waste time, money, and effort but they can also have a negative impact on your email deliverability rates. This is because if your business has a high bounce rate, servers may mark your emails as untrustworthy and begin to automatically block them or send them to spam.

Because of this, it’s very important to make sure that you are monitoring bounced emails and cleaning your email list regularly.

Hard and Soft Email Bounces

There are two main types of email bounces – soft or hard bounces. One is temporary, and the other is permanent.

Soft Bounces: In the case of a soft bounce, this means that the email address is valid, and the message was delivered to the inbox. However, the bounce occurred because the mailbox was full, the message was too large for the inbox, or the server was down.

It is generally considered to be a temporary issue as it can be rectified if the server is fixed, the recipient cleans their inbox, or if you reduce the size of the message.

Hard Bounces: A hard bounce will occur when an email is completely rejected due to the email address not existing or being otherwise invalid.

This is a permanent situation, and any email addresses that come back with a hard bounce should be removed from your mailing list to avoid having this situation happen again.

Common Reasons Why Emails Don’t Get Delivered

There are various different reasons why an email might bounce. Some of the most common ones include:

1 – The Email Address Does Not Exist

A bounce that is marked as a non-existent email address may have happened when the person who had the email address left the organization and the contact was deleted, or if you have send a message to an email address that is not spelt correctly.

There is also the chance that the recipient might have given a false email address, which might be the case if you are collecting contact information through an online sign-up form.

2 – Undeliverable Email

This bounce category will usually be a soft bounce. When a bounced email is in the ‘undeliverable’ category, this usually indicates that the receiving email server is overloaded, couldn’t be found or is temporarily unavailable.

In many cases, when the server cannot be found this might simply mean that it has crashed or is currently down for maintenance. In this case, it will usually just mean waiting for a while to try and send the email again. However, if you notice that an email address repeatedly bounces for this reason, it might mean that the server is down for good.

3 – Auto-Reply

If somebody has gone on holiday and has set an auto-reply function, any emails that you send to them will bounce. However, it is important to note that unlike other bounce categories, your email will still be successfully delivered to the inbox on this occasion.

However, it might be worth monitoring how often this email address gets an auto-reply bounce; if it’s been months and the person doesn’t seem to be coming back any time soon then you might want to consider removing the contact from your list.

4 – Full Mailbox

If you are sending an email to a contact that has so many emails in their inbox that they are unable to receive any more, then any messages you send to them are going to bounce. However, this is usually temporary, and you will be able to successfully deliver an email to the recipient when their inbox has enough space for it.

It is important to monitor, as it might mean that contact is no longer checking that address.

5 – Blocked Email

When email addresses are placed in the ‘blocked’ category, this means that the incoming email has been blocked by the server. This is often a common occurrence among schools or government agencies where servers are often stricter when it comes to the emails that they receive, which is why implementing a reliable school help desk software can greatly improve communication and streamline technical support processes.

6 – Spam Filter

In some cases, spam filters might be the reason behind a spike in undelivered emails. If you are using a blacklisted email address or IP address, then none of the messages that you send in bulk are likely to be delivered to and received by the recipients.

7 – Incorrect File Attachment

The majority of email hosting providers have restrictions regarding the type and size of file attachments. These can apply to both the client that you are sending the message from and the recipient. Most of the time, this is due to an incorrect file size, with the majority of this type of bounce occurring due to attachments that are too large.

8 – Greylisting

Greylist is a certain type of spam filter that does not allow the email to be delivered for a short amount of time. This might be 900 seconds or less. When this happens, you will usually receive a bounce back code to inform you of the situation. Once the time frame has passed, the server issues a second request and completes the delivery process.

9 – Poor Sender Reputation

Finally, if there are no obvious reasons for why an email has bounced such as a large attachment or the email no longer existing, and you are noticing other deliverability issues, your sender score might be to blame.

The sender score or reputation score refers to the way that email addresses are viewed by ISP. If you have a low sender score, then many, if not all of your messages will never actually get to the intended inboxes.

How to Reduce Your Email Bounce Rate

A high bounce rate is not good for your email list, with a big impact on deliverability and the overall success of your email marketing campaigns. It is important to monitor your bounce rate closely and be ready to take the next step if you are seeing some email addresses continually bounce.

Using an Email Tester

One of the best ways to keep your bounce rate low before you start sending marketing emails is to use an email testing tool before you start sending messages to your recipients. Testing your email list allows you to figure out if you have any issues that are likely to lead to a hard bounce like false email addresses, invalid email addresses, spelling mistakes and typos or email addresses that do not exist.

How a Deliverability Tester Can Help You Avoid Bounces

A deliverability tester can help you get a clearer idea of which email addresses are likely to receive your messages and which will be more likely to bounce. When an email address comes back as invalid or non-existent, you can easily remove it from your list without the need to send an email and risk increasing your bounce rate.

A deliverability testing tool will help you determine which email addresses are suspended, non-existent or undeliverable, so that you can immediately unsubscribe them from your list.

Once you have removed the email address, you may want to consider getting in touch with the intended recipient in a different way to see if their email address has changed and send them a link to a lead generation landing page that allows them to sign up with their new, correct email address.

Validation Tester – What’s the Best Method?

Along with tools that you can use to run a test on all the email addresses you have collected for your list to check any that are inaccurate or no longer existent, double opt-in is another way that you can make sure you are only sending out emails to recipients that are validated and want to receive messages from you.

The easiest way to do this is to set up an automatic confirmation email that is sent to any email addresses that are entered into your opt-in form, with a link for the recipient to click to confirm that they are actually signing up for your list and want to receive further communications from you.

Once you have done this, you should only add an email address to your list once you receive confirmation that the recipient has followed the link in the email.

Emails can bounce for many reasons. More often than not, it is a temporary issue such as a full inbox or a large file that can be fixed. However, hard bounces due to incorrect email addresses, for example, can cause serious damage to your sender score and lead to further bounces in the future.

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