IP address

An IP address is a unique identifier assigned to a device on a network. In the context of email, the IP address refers to the sending server’s origin point – used by inbox providers to evaluate sender identity, reputation, and trustworthiness. 

There are two types of sending IPs: 

• Dedicated IPs: Used by a single sender; reputation is fully controlled by that sender’s behavior 
• Shared IPs: Used by multiple senders; reputation is affected collectively 

Inbox providers use IP reputation – based on bounce rates, complaint rates, spam trap hits, and engagement – to determine whether messages are delivered, throttled, or blocked. 

Proper warm-up, authentication, and consistent sending behavior are critical for maintaining a healthy IP reputation whether that IP is shared or dedicated.