Hosting Industry News & Blog

Why do Emails Bounce Back?

Contributor: Ellyse Dwyer

Date: 24 May 2021

Why do Emails Bounce Back?

Email Bouncebacks are a common occurrence, they happen to everyone. You maybe have received multiple bouncebacks and they sometimes can be confusing and convoluted. First, If you are unable to work out why an email is bouncing, it’s important to contact our support team so can make sure all of your emails are delivered. But, it is also important to know what causing and what an email bounce message is.

So, lets get into the nitty gritty.

What is an email bounce?

An email bounce is an error message you receive when email you have sent is not delivered. Your email account will typically receive a Non-Delivery Report (NDR) instantly after sending an email or 72 hours depending on the type of bounce back, which we will get into later. These NDR also informs you what caused delivery failure of your email and are extremely important because they detail all the information for troubleshooting.

When you send out an email, the email is sent out via an SMTP server for delivery. The SMTP server checks your email with the DNS. The DNS is an address book for domain names and server IP addresses, like the yellow pages for the addresses on the internet. Once the recipient’s server is located, the SMTP server gives your message to their MTA to complete email delivery. This will allow the email to be delivered successfully.

However, sometimes the email may run into an issue during this process. This is where the bounce back messages come into play by telling yourself (the sender) what went wrong.

What causes the bounce back message?

There a multiple reasons for email bounce backs including full inboxes, servers that are not responding, send to email addresses that no longer exist, or something as simple as misspelling the email address.

There are three types of bounce backs:

  • Soft bounce emails
  • Hard bounce emails
  • Blocklisted emails

Soft Bounce Emails

Emails soft bounce is when a server rejects an email temporality. Most email services try to resend email messages after they soft bounce. You will typically see that it will reattempt in 24 hours or 72 hours.

Reasons for a soft bounce include:

Mailbox full: If the recipient mailbox has reached capacity and will bounce until there is free space to deliver.

Email Size: The email attachment may exceed the server or mail client limit, or it might be bounced back if there is a filter in place.

Server is down: An unreachable server may have crashed, be overloaded, or be under maintenance.

Hard Bounce Emails

A hard bounce happens when your email is permanently undeliverable to an email address.

Reasons for a hard bounce include:

Incorrect email address: This is a simple one but happens to the best of us. This the email address is spelt incorrectly you will receive the bounce back message.

Email blocked: Some domains have stricter spam filter settings. The recipient may have strict ruling in place. You will need to contact our support team regarding this issue.

You cannot fix hard bounce email issues what you can do is remove the reason behind the hard bounce, such as an incorrect email address.

Blockedlisted Emails

Email blocklists are created by ESPs to filter harmful or exploitative content, like spam or malware. It is not created to make it harder to spend emails, it is designed to protect the recipients of the emails sent daily.

Bounce back mxtoolbox

You can test your email against blacklists using helpful tools such as

Reasons for a Blocklisted include:

Spam complaints: An email may become compromised by a malicious attacking causing large volumes of spam. This may find you on a blocklist.

High bounce rates: Another reason may be just too many bounce backs by the reasons mentioned before.

Bad content: If you use certain words in your subject that are typically found in a Spam. You may find yourself on this list.

So, How do you get off a blocklist?

With time: The block maybe removed automatically after a predetermined time.

Contact the blocklist: A request can be sent to the blocklist holder’s website to be delisted.

Contact us:If you are unsure and need help removing yourself off a block listed, contact our support team so we may look on a server level.

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