/ Glossary — Infrastructure
What is a shared IP?
A sending address used by several senders at once, pooling their reputation. The right choice for low volume, a liability at scale. Here's the trade-off and how it compares to a dedicated IP.
/ Definition
A shared IP is a sending IP address used by multiple senders at the same time, typically managed by an email platform that routes many customers' mail through the same pool of addresses. Because reputation attaches to the IP, everyone on a shared IP shares its reputation — the good behavior of established senders helps you, and the bad behavior of others can hurt you.
The opposite is a dedicated IP, which you use alone. Shared IPs aren't inferior — for low-volume senders they're usually the better choice, because the pooled volume keeps the IP warm and the platform manages its reputation. The trade-off is control: you benefit from the pool's reputation but you're also exposed to it.
/ In practice
When a shared IP makes sense
Shared IPs suit senders whose volume is too low to maintain a dedicated IP's reputation on their own. Mailbox providers judge reputation partly on consistent volume, and an IP that sends only occasionally never establishes a stable reputation — it looks suspicious each time it wakes up. On a shared IP, the combined volume of many senders keeps the address consistently active and warm, and the platform handles the work of keeping the pool clean. For most senders below a few thousand messages a day, this is the pragmatic choice.
The reputation trade-off
The cost of sharing is shared fate. If another sender on your IP sends spam or hits spam traps, the IP's reputation suffers and your mail can be caught in the fallout — even though you did nothing wrong. Quality platforms mitigate this by segmenting good senders away from risky ones and policing their pools, but the structural exposure remains. As your volume grows, the point comes where a dedicated IP — whose reputation is yours alone to build and protect — becomes worth the responsibility it carries.
/ How shared pools are managed
Segmentation and policing
A well-run shared pool isn't a free-for-all. Quality platforms actively manage their pools to protect the senders on them: they segment good senders away from risky or new ones, monitor the pool's reputation continuously, and remove or isolate accounts that send spam or generate complaints before they can damage everyone else. Some maintain multiple pools tiered by sender quality, so established clean senders aren't mixed with unproven ones. This management is the real value a platform adds to a shared IP — it's why a shared IP on a reputable platform can outperform a poorly-maintained dedicated one, and why the operator's quality matters as much as the shared-versus-dedicated choice when either could work. Operator quality matters.
/ Related terms
Shared or dedicated is a volume question. We help you read it right.
We assess whether your volume justifies a dedicated IP or whether a shared pool serves you better, then operate either correctly. Bring us your sending profile.
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