What is shared vs dedicated infrastructure?

So when When you sign up with an ESP, one of the most consequential decisions is whether you're sharing sending resources with hundreds of other senders or getting your own. That's the shared vs dedicated infrastructure question, and it affects your reputation, your control, and your costs more than most people realize.

Shared infrastructure means your emails go out through IP addresses and servers that your ESP also uses for other customers. Think of it like an apartment block. Your behavior affects the building's reputation, and your neighbors' behavior affects yours. If another sender on the same shared IP pool triggers spam complaints, your deliverability can dip too. Most small and mid-size senders start here because it's included in the base plan and requires no setup.

Dedicated infrastructure means you get IP addresses (and sometimes a separate MTA) that only your sending uses. Your reputation is entirely your own. You're not carrying anyone else's baggage. The trade-off is that a fresh dedicated IP has no reputation at all, which means you have to warm it up before you can send at full volume. Skip the warmup and mailbox providers will be suspicious of a brand-new IP suddenly blasting thousands of emails.

The practical question is: which one is right for you?

• Shared IPs make sense when you're sending under 100,000 emails per month, your list is healthy and engaged, and you don't want to manage reputation yourself. ESPs like Mailchimp, Brevo, and MailerLite maintain shared pools with strong collective reputations, so new senders actually benefit from riding the established goodwill.
• Dedicated IPs make sense when you're sending high volume consistently, you have a clean list and strong engagement, and you want full control over your sending reputation. Postmark, Twilio SendGrid, and Mailgun all offer dedicated IP options at higher tiers.

One thing worth knowing: dedicated doesn't automatically mean better. A dedicated IP with poor list hygiene, low engagement, and inconsistent sending patterns will develop a worse reputation than a well-managed shared pool. The IP is neutral. What you do with it is what counts.

A lot of senders also use a hybrid approach. Transactional emails (receipts, password resets, alerts) go out on a dedicated IP to protect that clean reputation, while marketing campaigns run on shared or a separate dedicated pool. That way, a batch-and-blast campaign that generates complaints doesn't drag down your transactional stream with it.

Not sure what setup you're currently on? Your ESP's account settings usually show whether you're on a shared pool or a named dedicated IP. Or run your sending IP through our free blocklist checker to see what kind of reputation it carries right now.