Do all ESPs deliver the same way?

You send two identical campaigns. Same list, same content, same subject line. One lands in the inbox. The other lands in spam. What changed? The ESP.

No, ESPs don't all deliver the same way. The differences start with IP infrastructure. Some ESPs send from shared pools alongside thousands of other senders. If someone else on that pool starts spamming, your reputation gets caught in the crossfire. Others offer dedicated IPs where your sending history is entirely your own. The gap between a well-policed shared pool and a neglected one is very real.

Then there's how ESPs handle the conversation with mailbox providers. Gmail, Outlook, and Yahoo Mail each have different rate limits and different expectations. A good ESP adjusts sending speed per provider and keeps transactional email on separate infrastructure from marketing. A cheap one fires everything at full speed and hopes for the best.

Authentication is another place where ESPs split. Some automate SPF, DKIM, and DMARC for you. Others expect you to dig into DNS records yourself. And a few still default to signing with their own domain instead of yours, which quietly weakens your authentication profile without making it obvious.

Where you really feel the difference is in bounce and complaint handling. ESPs like Mailchimp, Smaily, and Postmark suppress hard bounces and process complaint feedback immediately. Budget providers may lag on this, letting bad addresses stack up and quietly drag your sender reputation down over time.

Your sending habits matter most. But two identical campaigns sent through two different ESPs can produce measurably different results. The infrastructure underneath you is doing real work, even when you can't see it.

If you're trying to figure out which ESP setup is right for your situation, our SOS hotline is free and we'll give you a straight answer with no sales pitch.