There are various reasons as to why an email may hard bounce. The most common reason is that the domain name does not exist or the recipient is unknown.  This may be due to misspellings in your address list, to recipients changing email providers, or to businesses closing.

Addresses that hard bounce may be considered bounced-out addresses and emails will not be sent to them again. This is based on the value set under Delivery Management in your General Settings.

Soft bounces usually indicate a temporary delivery issue, such as the recipients inbox being full or the receiving email server being down.

Soft bounces are handled differently than hard bounces. When a soft bounce occurs, the system will attempt to resend the same email over a 2-4 day period. If the email continues to soft bounce consistently, it will be counted as one hard bounce after that period.

A block bounce occurs when the email server rejects the email due to filter issues. These issues could include URL blocks, a lack of proper authentication, or blacklisting.

While block bounces are reported as hard bounces in your delivery statistics, they are not handled by your hard bounce settings. This means subscribers will not bounce-out of your mailing audience due to a blocked bounce.

The table below provides a list of Bounce Codes and additional information, such as bounce descriptions and if delivery retries will be attempted.