Transactional Email · Integration
Resend
Add Resend to your product for your customers, and give your AI agents governed access to it.
Resend is an email API for the mail a product cannot afford to lose, and the surface is small on purpose: emails and batch sends, domains, audiences and contacts, broadcasts, and a webhook that reports what happened to every message. That webhook is the reason it belongs next to a marketing platform rather than in a queue, because delivery, opens, clicks, bounces and complaints arrive as events and your product can answer why a user never got their invitation instead of assuming it landed. Domain verification is the other per-customer fact: DKIM and SPF records live in the customer's own DNS, so a send from an unverified domain fails before it leaves. Sends take an idempotency key, so a retry does not deliver twice. fastn holds each API key per tenant.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let each customer send from their own verified domain, so mail comes from them and their DKIM and SPF records are the ones being checked.
Send transactional mail and batches from your product with an idempotency key, so a retry after a timeout does not send twice.
Consume the delivery, open, click, bounce and complaint events so your product can tell a user what happened to a message.
Add a contact to an audience or send a broadcast when something in your product warrants it.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent explains why a message never arrived by reading its bounce or complaint event.
An agent sends an approved message on a customer's behalf within scoped permissions, with the send logged.
An agent reports which domains a customer has verified and which are still waiting on DNS.
Example prompt
Did this invitation reach the user, and if it bounced, what reason came back with the event?
Set up Resend in 4 steps
- 01Enable the Resend connector in your fastn dashboard.
- 02Have each customer supply their own API key and verify the sending domain in their DNS.
- 03Map the templates or payloads you send, subscribe to the delivery and engagement events you act on, and set your idempotency keys.
- 04Call it from your product and expose the same connection to your agents through the MCP gateway.
Why teams use the Resend integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Resend integration without building it. Your customers connect their own Resend account inside your product and work their messages, templates and delivery events there, with no per-customer code on your side.
- Handle the part that actually costs time: deliverability is the whole game, and it is decided by bounces, complaints and the reputation of the sending domain rather than by anything in the send call. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Resend update is not your on-call problem.
- One integration serves your product and your agents. The same governed Resend connection powers in-product features and gives AI agents scoped, audited access, so you send the mail your product owes its users and know what happened to it without wiring it twice.
Used by these teams
Works well with
SendGrid
Klaviyo
TwilioOften used alongside
Tools the same teams tend to run next to Resend, across other categories.
Notion
Box
Shopify
StripeResend integration FAQ
How do I add a Resend integration to my product?
Enable the Resend connector in your fastn dashboard, then let each customer authenticate their own Resend account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Resend client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Resend account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Resend account and only ever sees their own messages, templates and delivery events. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Resend integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent explains why a message never arrived by reading its bounce or complaint event.
Who maintains the Resend integration?
fastn does. When Resend changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Can each customer send from their own domain with Resend?
Yes, and it is the reason to do this per tenant rather than through one shared key. Sending reputation attaches to the domain, so a customer sending from their own verified domain in Resend carries their own deliverability rather than inheriting yours or damaging it.
How do bounces and complaints come back from Resend?
As records rather than log lines. Hard bounces, spam complaints and unsubscribes become suppression state you can read per tenant, so your product can stop mailing an address that already failed instead of sending into a hole and quietly burning the customer's sending reputation.
What can I build with the Resend integration?
A common starting point: let each customer send from their own verified domain, so mail comes from them and their DKIM and SPF records are the ones being checked. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Resend integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Resend does not change your per-connector cost. You can start free with 3 connected accounts.
Add Resend to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.