What is a shared IP pool?

A shared IP pool is a group of IP addresses your ESP uses to send email for hundreds (or thousands) of customers at once. You don't get your own IP. You share it with everyone else on the platform.

But Here's how it works. When Mailchimp, Brevo, or any other ESP sends your email, it goes out from one of their shared IPs. Mailbox providers (Gmail, Outlook, Yahoo) track the reputation of that IP based on ALL the email it sends, not just yours. If the pool's reputation is good, your email gets delivered. If the pool's reputation tanks because someone else is spamming from it, your email gets caught in the crossfire.

The main risk is what people call the noisy neighbor effect. One bad sender in the pool sends spam, triggers complaints, or hits spam traps. The IP's reputation drops. Now everyone sharing that IP sees worse delivery, even if their own practices are clean. You can't control who your neighbors are or what they send.

But That said, shared IPs aren't inherently bad. Most ESPs actively monitor their shared pools and remove abusive senders quickly. If you're sending under 50,000 emails a month with good engagement, a shared pool is usually fine. The collective volume helps maintain the IP's reputation, and you're not responsible for warming up a fresh IP yourself.

Most new senders start in shared pools by default. Your ESP assigns you to one automatically. To move to a dedicated IP, you usually need consistent volume (50k+ emails/month), clean engagement metrics, and willingness to pay extra (dedicated IPs cost $20-$100/month depending on the ESP). If your volume is lower or inconsistent, staying in a shared pool is often the smarter choice.

You can't see which IP pool you're in without asking your ESP or checking email headers. If delivery suddenly drops for no clear reason, one possibility is pool contamination. Worth checking your recent campaign metrics and asking your ESP support team if there's been a pool issue. (They won't always tell you proactively.)