Do all ESPs deliver the same way?

Myth: False. ESPs differ significantly in how they move your email from their servers to the recipient's mailbox.

The most visible difference is IP infrastructure. Some ESPs send your email from shared pools alongside thousands of other senders — if someone else on your pool spams, your reputation takes the hit. Others offer dedicated IPs where your reputation is entirely yours. The gap between a well-policed shared pool and a neglected one is enormous.

Then there's how ESPs talk to mailbox providers. Gmail, Outlook, and Yahoo each have different rate limits and expectations. Sophisticated ESPs dynamically throttle per provider and maintain separate delivery paths for transactional versus marketing email. Others blast everything at full speed and hope for the best.

Authentication setup varies too. Some ESPs automate SPF, DKIM, and DMARC entirely. Others require you to configure DNS records manually. A few still default to signing with their own domain instead of yours, which weakens your brand's authentication profile.

Where you really feel the difference is bounce and complaint handling. ESPs like Mailchimp, Smaily, and Postmark suppress hard bounces and process FBL complaints immediately. Budget providers may delay or skip this entirely, letting bad addresses pile up and drag down your sender reputation.

Your sending practices still matter most. But two identical campaigns sent through two different ESPs can produce measurably different results.