Why It Matters
Most email platforms start you on a shared IP by default. That's not necessarily bad — reputable ESPs carefully manage their shared IP pools and kick off senders who misbehave. But if a bad actor on your shared IP sends spam, the resulting blacklisting affects you too. It's a tradeoff: lower cost and no warmup period, but less control over your reputation.
How It Works
Your ESP assigns outgoing mail from your account to one or more IPs in a shared pool. Those same IPs carry mail from dozens or hundreds of other senders. Mailbox providers evaluate the IP's overall behavior, not just yours. If the pool maintains a strong reputation (low complaints, low bounces), everyone benefits. If someone in the pool starts blasting purchased lists, everyone suffers.
Quick Tips
- Shared IPs work well if you send under 50,000 emails per month — the ESP's pool reputation does the heavy lifting.
- If you notice sudden deliverability drops without changing your own behavior, your shared IP might be the culprit. Ask your ESP.
- Once you consistently send 100K+ emails monthly, it's usually worth moving to a dedicated IP for full control.