Shared IP
A shared IP is an email sending IP address used by multiple accounts on the same email service provider. All senders on the shared IP contribute to and are affected by the IP's overall reputation. Good providers monitor shared IP pools and isolate or remove bad senders to protect the group.
Pros and Cons
Advantages: No warmup needed (the IP already has established reputation), lower cost, good for low-volume senders.
Disadvantages: Your deliverability can be affected by other senders on the same IP. If a co-sender gets flagged for spam, your emails may also be blocked or throttled.
Modern platforms mitigate shared IP risks through reputation isolation, where each sender's reputation is tracked separately even on shared infrastructure, preventing one bad actor from affecting others.
Related Terms
Dedicated IP
An IP address used exclusively by one sender, giving full control over sending reputation.
IP Reputation
The trustworthiness score assigned to an IP address based on its email sending history.
Reputation Isolation
The practice of separating sender reputation to prevent one sender's bad practices from affecting others.
Need help with email deliverability?
Transmit handles authentication, warmup, and reputation isolation automatically.