Use the SDK
you already know.
Connect the Resend Node SDK to ZapSMTP using environment variables. Check the endpoints and event handlers your application uses before changing production traffic.
Verify your domain and create a key
Add your domain and publish the records supplied in the dashboard. Store your ZapSMTP API key on the server. Keep your existing provider’s DNS records while both integrations are in use.
Configure the SDK
The Node SDK reads RESEND_BASE_URL from the server environment. Set it to the compatible API base URL supplied with your ZapSMTP account and use a ZapSMTP key as RESEND_API_KEY.
Use a test key and verify your SDK version’s send, batch, scheduling, template, and attachment requests before switching traffic.
Reconnect event handlers
Create webhook endpoints in ZapSMTP and configure their signing secrets in your backend. Test signature verification, retries, and the delivery, bounce, complaint, and inbound events you handle.
Keep suppression history
Add your existing bounces, complaints and unsubscribes with the suppressions API before switching traffic. Addresses are added individually with POST /v1/suppressions.
Change traffic gradually
Start in the sandbox, then test a small production batch. Inspect events and failure handling before increasing volume.