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| title: "Resend email agent with Slack approval" | ||
| sidebarTitle: "Resend email agent" | ||
| description: "An AI agent that drafts replies to a Resend inbox and sends nothing until you approve it in Slack. Uses hosted webhooks for Resend and Slack, and wait tokens to pause each email thread until you click Send." | ||
| --- | ||
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| <iframe | ||
| width="100%" | ||
| height="315" | ||
| src="https://www.youtube.com/embed/6GjXLwj_dnE" | ||
| title="Resend email agent with Slack approval" | ||
| allow="accelerometer; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" | ||
| referrerPolicy="strict-origin-when-cross-origin" | ||
| allowFullScreen | ||
| /> | ||
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| ## Overview | ||
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| This agent drafts replies to the email in a [Resend Inboxes](https://resend.com/docs/api-reference/inboxes) inbox and posts each draft to your Slack DMs for approval. Every email chain gets its own Slack thread. Click **Send** to reply from the inbox address, **Don't send** to drop the draft, or reply in the thread ("shorter", "say we're closed over Christmas") to get a new draft. Later emails in the same chain land in the same Slack thread. | ||
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| **Tech stack:** | ||
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| - **[Trigger.dev webhooks](/webhooks/overview)** receive Resend and Slack events and verify their signatures | ||
| - **[Wait tokens](/wait-for-token)** pause each email thread's run until you act in Slack | ||
| - **[Resend Inboxes](https://resend.com/docs/api-reference/inboxes)** receive email and send the approved replies | ||
| - **[AI SDK](https://ai-sdk.dev)** drafts replies through the [Vercel AI Gateway](https://vercel.com/docs/ai-gateway) | ||
| - **[Slack](https://api.slack.com)** for the DM-only approval app | ||
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| **Features:** | ||
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| - **A person sends every reply**: the model has no tools, so a hostile email can only change the words of a draft you read first. | ||
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| - **Feedback in the thread**: replying to a draft writes a new one that takes your note into account. | ||
| - **One run per email chain**: a run waits days for your click without holding a machine or a concurrency slot. | ||
| - **Sender allowlist**: `ALLOWED_SENDER_DOMAINS` drops unknown senders before they reach Slack or cost a model call. | ||
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| - **Idempotent sends**: each inbound email gets at most one reply, even when a run retries. | ||
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| ## GitHub repo | ||
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| <Card | ||
| title="View the Resend email agent repo" | ||
| icon="GitHub" | ||
| href="https://github.com/triggerdotdev/examples/tree/main/resend-slack-email-agent" | ||
| > | ||
| Click here to view the full code for this project in our examples repository on GitHub. You can | ||
| fork it and use it as a starting point for your own project. | ||
| </Card> | ||
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| ## How it works | ||
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| Each email chain gets one long-running `email-thread` run that sleeps on a wait token between events. The token is tagged with the email thread id and the Slack message timestamp, so a webhook from either side can find it and wake the run. | ||
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| ```mermaid | ||
| flowchart LR | ||
| E([New email]) --> R[resend-email-received<br/>webhook task] | ||
| C([Button click]) --> S[slack-activity<br/>webhook task] | ||
| T([Thread reply]) --> S | ||
| R -- wakes or starts --> RUN[email-thread run<br/>waits on a token] | ||
| S -- completes token --> RUN | ||
| RUN -- email, draft, buttons --> DM[Your Slack DM] | ||
| RUN -- after you click Send --> SEND[Resend reply] | ||
| ``` | ||
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| ### Hosted webhook endpoints | ||
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| Two endpoints receive events, one for Resend and one for Slack. Trigger.dev checks each request's signature before your code runs, and the Slack source answers Slack's `url_verification` handshake. | ||
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| ```ts src/trigger/endpoints.ts | ||
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| import { webhooks } from "@trigger.dev/sdk"; | ||
| import { webhookSource, type SlackBlockActions, type SlackMessageEvent } from "@trigger.dev/slack"; | ||
| import type { ResendWebhookEvent } from "./resend"; | ||
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| export const resendEvents = webhooks.endpoint.define({ | ||
| id: "resend", | ||
| source: webhooks.resend<ResendWebhookEvent>(), | ||
| }); | ||
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| export const slackEvents = webhooks.endpoint.define({ | ||
| id: "slack", | ||
| source: webhookSource<SlackMessageEvent | SlackBlockActions>(), | ||
| }); | ||
| ``` | ||
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| ### Waiting for approval | ||
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| After posting a draft, the run creates a wait token and waits on it. The token is created before the draft is posted, so a fast click always has something to complete. Each button carries the token id. | ||
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| ```ts src/trigger/email-thread.ts | ||
| const token = await wait.createToken({ | ||
| timeout: "30d", | ||
| tags: [emailTag(threadId), slackTag(slackTs)], | ||
| }); | ||
| draftTs = await post(channel, "Draft reply", draftBlocks(draft, token.id), slackTs); | ||
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| const result = await wait.forToken<Signal>(token); | ||
| ``` | ||
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| ### Waking the run | ||
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| The webhook tasks find the waiting token by tag and complete it with what happened: a button click, a reply in the thread, or a new email. The run then sends the reply, drops it, or redrafts with your note, and waits again. | ||
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| ```ts src/trigger/inbound.ts | ||
| const token = await waitingToken(slackTag(msg.thread_ts)); | ||
| if (token) await wait.completeToken<Signal>(token, { kind: "feedback", user: msg.user, text }); | ||
| ``` | ||
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| ## Running the project | ||
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| You need a Trigger.dev project, a Resend inbox on a verified domain, a Slack workspace where you can create apps, and a Vercel AI Gateway key. | ||
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| <Steps> | ||
| <Step title="Clone the example and install"> | ||
| ```bash | ||
| git clone https://github.com/triggerdotdev/examples.git | ||
| cd examples/resend-slack-email-agent | ||
| cp .env.example .env | ||
| pnpm install | ||
| ``` | ||
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| Set `TRIGGER_PROJECT_REF` in `.env` to your project's ref, from the project settings page in the dashboard. Then run `pnpm dev`, which adds two endpoints, `resend` and `slack`, to your dev environment's **Webhooks** page. | ||
| </Step> | ||
| <Step title="Connect Resend"> | ||
| Add a Resend webhook pointing at the `resend` endpoint URL with the `inbox.email.received` event. Paste its signing secret into the `resend` endpoint, and set `RESEND_API_KEY`. | ||
| </Step> | ||
| <Step title="Connect Slack"> | ||
| Put the `slack` endpoint URL in `slack/manifest.yaml` and create the app from it. Paste its Signing Secret into the `slack` endpoint, click **Verify** in Event Subscriptions, install the app, and set `SLACK_BOT_TOKEN`. | ||
| </Step> | ||
| <Step title="Set who approves and who can email"> | ||
| Set `SLACK_USER_ID` to your Slack member ID, `ALLOWED_SENDER_DOMAINS` to the domains you accept email from, and `AI_GATEWAY_API_KEY`. Restart `pnpm dev`. | ||
| </Step> | ||
| <Step title="Send a test email"> | ||
| Email your inbox from an allowed address. A DM from the bot shows the email with a draft in its thread, and the dev terminal shows a `resend-email-received` run followed by an `email-thread` run that stays waiting. | ||
| </Step> | ||
| </Steps> | ||
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| To deploy, run `npx trigger.dev@latest deploy` and set the same environment variables on your production environment. Production has its own `resend` and `slack` endpoints, with their own URLs and secrets: point a Resend webhook and a Slack app at the production URLs, and paste each one's signing secret into the matching production endpoint. Until then, the endpoint shows "Needs secret" on the Webhooks page. | ||
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Contributor
There was a problem hiding this comment. Use the production Slack app’s bot token. If a reader creates a separate Slack app for production, copying Prevent both environments from processing the same inbox. If a reader creates a production Resend webhook while the development webhook and |
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| ## Relevant code | ||
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| - **Email thread task**: [src/trigger/email-thread.ts](https://github.com/triggerdotdev/examples/blob/main/resend-slack-email-agent/src/trigger/email-thread.ts): one run per chain that posts, drafts, waits on a token and acts on the result | ||
| - **Webhook tasks**: [src/trigger/inbound.ts](https://github.com/triggerdotdev/examples/blob/main/resend-slack-email-agent/src/trigger/inbound.ts): wake or start a thread's run from Resend emails, Slack clicks and thread replies | ||
| - **Drafting prompt**: [src/trigger/draft.ts](https://github.com/triggerdotdev/examples/blob/main/resend-slack-email-agent/src/trigger/draft.ts): the AI SDK call and the system prompt to tune for your inbox | ||
| - **Webhook endpoints**: [src/trigger/endpoints.ts](https://github.com/triggerdotdev/examples/blob/main/resend-slack-email-agent/src/trigger/endpoints.ts): the hosted Resend and Slack endpoints | ||
| - **Slack app**: [slack/manifest.yaml](https://github.com/triggerdotdev/examples/blob/main/resend-slack-email-agent/slack/manifest.yaml): a DM-only app with three scopes | ||
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| ## Learn more | ||
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| <CardGroup cols={2}> | ||
| <Card title="Webhooks" icon="webhook" href="/webhooks/overview"> | ||
| Hosted endpoints that verify and deliver events to your tasks. | ||
| </Card> | ||
| <Card title="Wait for token" icon="hourglass" href="/wait-for-token"> | ||
| Pause a run until an external event completes a token. | ||
| </Card> | ||
| <Card title="Webhook sources" icon="plug" href="/webhooks/sources"> | ||
| Every built-in source, including `resend()`, and how each is verified. | ||
| </Card> | ||
| <Card title="Slack" icon="slack" href="/webhooks/slack"> | ||
| The Slack source and channel in `@trigger.dev/slack`. | ||
| </Card> | ||
| </CardGroup> | ||
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