What is “IP reputation block”?

An IP reputation block is rejection based on sending IP history:

What it means:

Your sending IP has poor reputation. Past behavior flagged it as risky. Receiving servers refuse connections or messages from it.

How reputation is damaged:

Sending to spamtraps. High complaint rates. Sending to invalid addresses. Previous spam activity. Blocklist inclusion.

Detection:

Bounce messages reference IP or "sender reputation." Check tools: Sender Score, Google Postmaster Tools. Query blocklists directly.

Resolution:

Reduce sending volume temporarily. Remove problematic addresses. Monitor and improve engagement. Request blocklist removal. Consider IP warming or new IPs.

Prevention:

Maintain list hygiene. Monitor complaint rates. Warm new IPs properly.

IP reputation is your vessel's sailing record. Past incidents follow you to every port.