How are block bounces different from other hard/soft bounces?

Block bounces occupy a distinct category:

Hard bounces:

Address is permanently invalid. User does not exist, domain invalid. Action: Suppress immediately. Root cause: Bad address data.

Soft bounces:

Temporary delivery failure. Mailbox full, server busy. Action: Retry, then suppress if persistent. Root cause: Temporary conditions.

Block bounces:

Address is valid but sender is refused. Reputation, policy, or content issue. Action: Investigate and remediate. Root cause: Sender behavior or configuration.

Key differences:

Suppressing address does not fix block bounces. Block bounces require sender-side changes. May affect delivery to entire domain, not just one address.

Block bounces are about you, not the address. Fix yourself, not your list.