Does IP reputation carry across domains?
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Yes and no. IP reputation and domain reputation are separate scores, but they both factor into where your email lands. And if you're on a shared IP, what other senders do on that IP can absolutely affect your delivery, even if your own sending is squeaky clean.
Here's how it works. Every email you send comes from an IP address. Mailbox providers like Gmail and Outlook look at that IP's history. Lots of spam from that IP? Red flag for everyone on it. At the same time, they track your domain's behavior separately. So you can have a good domain reputation and still hit the spam folder because the shared IP you're on has a rough history.
Think of it like having a great personal credit score but sharing a business account with someone who defaults on everything. The bank knows you're not the problem, but it still makes lending to you riskier.
In practice, most ESPs put small and medium senders on shared IP pools. The quality of that pool depends on who else is sending from it. A good ESP curates their pools carefully and moves bad actors off quickly. A cheaper or less careful ESP might not, and you pay the price.
On a dedicated IP, you own the reputation entirely. That's good if you're sending well. It's also bad if you're not, because there's no one else to absorb the impact. New dedicated IPs start with zero history, which is actually riskier than a well-maintained shared pool at first.
If you're worried your IP's reputation is dragging you down, check it. Our free blocklist checker will tell you if your sending IP is listed anywhere it shouldn't be. If the problem is your ESP's shared pool quality, that's a harder conversation, and sometimes worth switching for.
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