Hard Bounce / Soft Bounce

A hard bounce refers to an email that is rejected by the recipient’s email server due to permanent reasons. This rejection typically occurs when the recipient’s email address or domain name does not exist, or when the recipient’s email server has completely blocked the delivery. Despite the validity of the email address, instances of hard bounces can still occur, indicating a definitive failure in email delivery.

Example

An example of a hard bounce is when an email is sent to an address like “nonexistent@example.com,” where “example.com” is a domain that doesn’t exist. Since the domain is invalid, the email server will permanently reject the message, resulting in a hard bounce.

Conversely, a soft bounce occurs when the recipient’s email server temporarily rejects the email due to issues like a full inbox or a temporary server problem. For instance, if an email is sent to an address that exceeds its storage limit, the server may temporarily reject the message, resulting in a soft bounce.