What’s the difference between “blacklist rejection” and “filtering”?

Blacklist rejection and filtering operate at different stages:

Blacklist rejection:

Occurs during SMTP conversation. Based on sender IP or domain reputation. Message refused before content evaluated. Immediate, definitive rejection. You receive a bounce or error.

Filtering:

Occurs after message acceptance. Based on content analysis. Message delivered but may go to spam. No explicit notification to sender. May vary per recipient.

Key differences:

Timing: Rejection is synchronous; filtering is post-acceptance. Visibility: Rejection is explicit; filtering is often silent. Basis: Rejection is reputation; filtering is content.

Implications:

Blacklist issues require reputation repair. Filtering issues require content optimization. Both require investigation but different solutions.

Blacklisting stops you at the gate. Filtering diverts you after entry.