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Case study · Shopify Plus checkout app · October 2025
Checkout Components sells checkout upgrades to Shopify Plus brands. For two weeks in October 2025 we sent their campaigns through two engines at once: Instantly, and the private sending server Charm builds for every client. Same leads, same copy, same domains. The only thing that changed was where the email went out from.
Higher reply rate on Charm, on every campaign in the test.
Reply rate on Charm across the four campaigns: 406 replies from 7,415 leads. Instantly ran between 0.85% and 1.95%.
Interested prospects from Charm’s sends. Instantly turned up none on three of the four campaigns.
The setup
Checkout Components sells to founders and ecommerce leads at single-store Shopify Plus brands, a buyer every checkout and upsell app is already emailing.
In cycle three we wrote the campaigns for those single-store merchants, then ran each one on both engines between October 15 and 31, 2025. Every campaign kept its subject line and body copy word for word on both sides, so the reply gap comes down to delivery.
The results
Reply rates from the Checkout Components cycle three performance report, sends from October 15 to 31, 2025. Interested counts are prospects who asked for the demo or said yes, from the Charm side.
Why the gap
Instantly puts you on shared servers. If the guy upstairs leaves his water running, your ceiling gets wet. Google and Microsoft know those IP pools, so one spammer on your server drags you down with him.
We build every client their own house, a private server nobody else sends from. Your sender reputation comes from your sends alone. When an inbox gets dinged, we swap in one we already warmed in reserve, so sending never waits.
Who raised a hand
Interested replies from the Charm side came from brands including:
“[Store] <> Checkout Components” had the smallest reply lift and produced 14 of the 21 interested prospects. It became the base campaign for the next two cycles, sent from Charm’s server.