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Deliverability

IP Reputation

A score assigned to a sending IP address based on email sending history and behavior.

Definition

IP reputation is a score assigned to an IP address based on its email sending history, complaint rates, bounce rates, spam trap hits, and engagement patterns. Mailbox providers use IP reputation to decide whether to accept, filter, or block emails from that IP. High reputation means better inbox placement; low reputation means spam filtering or blocking.

Why It Matters

IP reputation directly affects whether your emails reach the inbox. Sending from an IP with poor reputation can doom your campaigns regardless of content quality. Whether using shared IPs (common with ESPs) or dedicated IPs, reputation management is essential for deliverability.

How It Works

Every time emails are sent from an IP, receiving servers record the outcomes - bounces, complaints, engagement, spam trap hits. These aggregate into a reputation score. Major providers like Gmail, Microsoft, and Yahoo maintain their own reputation databases. Reputation builds over time and can be damaged quickly.

Best Practices

  • 1Monitor IP reputation using tools like Sender Score or Google Postmaster
  • 2Warm up new IPs gradually before high-volume sending
  • 3Maintain low complaint rates (under 0.1%)
  • 4Keep bounce rates low through list hygiene
  • 5Consider dedicated IPs for high-volume senders

Frequently Asked Questions

It depends. Shared IPs pool reputation across multiple senders - good if your volume is low, risky if others behave badly. Dedicated IPs give you full reputation control but require enough volume to maintain. Generally, dedicated IPs suit senders of 100k+ emails monthly.

Building positive reputation takes 4-8 weeks of consistent, good sending behavior. Start with low volume and gradually increase (IP warming). Damaging reputation can happen quickly; recovery takes longer than initial building.