How to fix Hard Bounces

What is a Hard Bounce?

SMTP2GO categorizes bounced emails as either 'Soft' or 'Hard' by analyzing the error message that is sent to us by the recipient's mail server. A hard bounce occurs when there is a permanent issue or there is no chance that the email address will work in the future.

Common causes for hard bounces can be due to a recipient's address being invalid or not existing, authentication issues (SPF/DKIM/DMARC), or due to spam filtering or reputation issues.

To view specific hard bounce reasons, go to your 'Reports > Activity' page, select the hard bounced email and then view the 'Timeline' tab. The 'Timeline' tab will show you the Hard Bounce message that we received from the recipient's incoming server. The responses differ depending on the recipient server but they often give a clear reason in regard to why the email failed.




Hard Bounce Examples

  • 550 5.5.0 Requested action not taken: mailbox unavailable
  • 550 5.4.1 Recipient address rejected: Access denied. AS(201806281)
  • 550 No Such User Here
  • 552 1 Requested mail action aborted, mailbox not found
  • 550 5.7.1 Message rejected due to SPF policy
  • 550 5.7.1 Sender ID (PRA) Not Permitted


What happens when a Hard Bounce occurs?

Our system automatically blocks (for 7 days) any attempt to send to an email address that has hard bounced. This is an important policy: if we continually tried to send emails to hard bouncing email addresses, we would very quickly damage our reputation in the email community. After 7 days, the hard-bounced email address will be automatically unblocked and sending can resume. If there are still issues with the recipient email address, however, it will hard-bounce time and time again. You should, therefore, remove hard-bouncing email addresses from your mailing list.

We record blocked attempts to send emails and call these rejected emails. Rejected emails are attempts to send emails to any email address that has hard-bounced within the past 7 days, has previously reported an email as spam, has previously unsubscribed, or has been manually added as a suppression. You should aim to have zero rejected emails.

If you find a hard bounce that you think may work again, you can unblock it from the 'Reports > Suppressions' page in your account.


How do I resolve a Hard Bounce?

The recipient will need to resolve the hard bouncing issue from their side. You may need to make alternative contact asking them to investigate and you can provide them with the bounce response their server is giving to help them resolve the issue. You can attempt to send an email to them again if they resolve the issue. Note: You will need to remove the address from your 'Reports > Suppressions page' if it is within 7 days of the original hard bounce.

Can a Hard Bounce be resent?

Once an email hard bounces, it won't be resent and there is no option to resend that from in the SMTP2GO account. The bounce is the final result for the email and it would need to be sent again from the sending software.

If you encounter bounces that you would like assistance with, please contact our support team with specific examples and we will investigate for you.



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