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Clean email lists to eliminate bounces and engage subscribers


Mayank AgarwalOct 7, 2021 7:23:08 AM4 min read

What is a Hard Bounce in Email Marketing?

An email bounce is an event when the email you send fails to get delivered to the recipient’s mailbox. The email is simply rejected by the recipient’s mail server. Email bounce is classified into two types:

Type of Email Bounce Definition Cause Action Item to Avoid It
Hard Bounce Permanent delivery failure of email
  • The recipient's address is invalid
  • The receiving server is blocking emails from your domain
  • Clean your list
  • Use the double-opt-in subscription form 
Soft Bounce Temporary delivery failure of email
  • Full mailbox
  • Email account suspended, temporarily 
  • Oversize email
  • Server timeout
  • Authentication failed
  • Authenticate your emails
  • Avoid free-sender domains
  • Monitor your email delivery
  • Resend emails

Let’s read on to explore in-depth what is hard bounce & soft bounce in email marketing. We will also see how you can handle these to ensure your emails are actually sent to people’s mailbox.

Hard bounce

Hard bounce definition: When the email you send fails to get delivered for permanent reasons, it is said to be hard bounced. Permanent reasons mean that even if you resend the email, it will not get delivered. It will be returned to the sender’s address with a failed delivery notification.







  • Recipient’s address is invalid: If the subscriber entered the email address as ‘’ instead of ‘’, then we know that even after re-trying the email won’t be sent because the email address simply doesn’t exist. Sometimes, people switch their providers e.g. a person may go from ‘’ to ‘’ and in that case too, their old email address will become invalid.
  • Receiving server is blocking emails from your domain or IP address: Some companies or governments have stricter restrictions on who can send emails to email addresses associated with their domain. If you have any email addresses from such companies or governments, then the email will not get delivered even after re-trying. It’s a permanent block.

How does hard bounce affect your email marketing?

The metric it affects is the delivery rate. The delivery rate is the percentage of emails that got delivered to the inbox out of all the emails you send.

If your delivery rate is constantly low, it will signal the spam filters of inbox providers (Gmail, Yahoo, etc.) that your email list is filled with invalid data and hence might not be from genuine signups. So emails will end up getting classified as ‘spam’ & your sender’s reputation will become low. Hence inbox providers will try to protect the valid email addresses from getting your supposedly ‘spam’ emails by sending those to the spam folder, instead of the inbox.

The action you can take to lower the number of emails that get hard-bounced:

  • Clean your list: People move jobs and change email addresses. Teenagers definitely change email addresses once they realize ‘’ is in fact… not such a cool email address. People also make typos sometimes and subscribe to the wrong email address. So you should clean your email list by removing email addresses that are no longer valid.
  • Use double opt-in: Sometimes, people make typos while signing up for your newsletter or lead magnet. There can also be a case of getting your subscription form hacked and someone signing up with invalid emails to hijack your website.  The sure-shot way to avoid this from happening is to send a confirmation email to people once they sign up for your emails. This ensures that the email address is not mistyped or invalid. It will also avoid people who are not genuinely interested to receive your emails from getting added to the list.

SendX takes email delivery seriously and hence automatically removes any hard bounced emails from future campaigns. Even if they are part of your broadcast list, we will not even try delivering email to those addresses as we know they will negatively impact your sender’s reputation.

You can also manually see all the hard bounced emails and delete them from the list, permanently.

A healthy bounce rate is below 2%. Anything higher than that will negatively impact your overall email delivery and sender’s reputation. Thus impacting the reach of your email.

Wrap Up

Here's a summary of action items for you to maintain a low soft & hard bounce rate:

  • Clean your list
  • Use double-opt-in
  • Authenticate your domain
  • Avoid free sender domains
  • Re-send soft-bounced emails
  • Monitor your email delivery rate

Please note that if your email goes into the spam box of the recipient, it is not considered a bounce. It is considered to be delivered but not just to the inbox. While bounced emails impact your 'delivery rate', an email going to the spam box negatively impacts your ‘deliverability rate’ which is the percentage of emails that go into the inbox and not the spam box.

If you want to read more about it, check out this article on email deliverability.



Mayank Agarwal

Mayank is an email marketing expert & co-founder of SendX. SendX is an intuitive & affordable email marketing software.