Soft and Hard Bounces

A bounce means a message could not be delivered. The response type determines what to do next.

Type	Meaning	Action
Soft bounce	Temporary failure, such as mailbox full or transient server issue.	Retry according to platform policy and monitor recurrence.
Hard bounce	Permanent failure, such as invalid recipient.	Suppress the address and stop sending.

Repeated soft bounces can become a reputation problem. Monitor both types.