Resend

Resend Email API

Send transactional emails, manage contacts, and domains via Resend's REST API.

Official docs: https://resend.com/docs/api-reference/introduction

When to Use

Use this skill when you need to:

• Send transactional emails (welcome, password reset, notifications)
• Send batch emails to multiple recipients
• Manage email contacts and audiences
• Verify and manage sending domains
• Track email delivery status

Prerequisites

1. Sign up at https://resend.com
2. Go to API Keys: https://resend.com/api-keys
3. Create a new API key

Set environment variable:

export RESEND_API_KEY="re_xxxxxxxxx"

Important: When using $VAR in a command that pipes to another command, wrap the command containing $VAR in bash -c '...'. Due to a Claude Code bug, environment variables are silently cleared when pipes are used directly.

Placeholders: Values in {curly-braces} like {email-id} are placeholders. Replace them with actual values when executing.

Emails

Send Email

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with Plain Text

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "text": "<your-plain-text-content>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with CC/BCC

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "cc": ["<your-cc-email>"],
  "bcc": ["<your-bcc-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with Reply-To

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "replyTo": "<your-reply-to-email>",
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Scheduled Email

Schedule email using natural language or ISO 8601 format:

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>",
  "scheduledAt": "in 1 hour"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Batch Emails

Send up to 100 emails in a single request:

Write to /tmp/resend_request.json:

[
  {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["<your-recipient-1>"],
    "subject": "Hello 1",
    "html": "<p>Email 1</p>"
  },
  {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["<your-recipient-2>"],
    "subject": "Hello 2",
    "html": "<p>Email 2</p>"
  }
]

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails/batch" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Retrieve Email

bash -c 'curl -s "https://api.resend.com/emails/<your-email-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

List Sent Emails

bash -c 'curl -s "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY"'

Cancel Scheduled Email

bash -c 'curl -s -X POST "https://api.resend.com/emails/<your-email-id>/cancel" --header "Authorization: Bearer $RESEND_API_KEY"'

Contacts

Create Contact

Write to /tmp/resend_request.json:

{
  "email": "<your-contact-email>",
  "firstName": "<your-first-name>",
  "lastName": "<your-last-name>",
  "unsubscribed": false
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Create Contact with Custom Properties

Write to /tmp/resend_request.json:

{
  "email": "<your-contact-email>",
  "firstName": "<your-first-name>",
  "lastName": "<your-last-name>",
  "properties": {
    "company": "<your-company-name>",
    "role": "<your-role>"
  }
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Retrieve Contact

bash -c 'curl -s "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

List Contacts

bash -c 'curl -s "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY"'

List Contacts with Pagination

bash -c 'curl -s "https://api.resend.com/contacts?limit=50" --header "Authorization: Bearer $RESEND_API_KEY"'

Update Contact

Write to /tmp/resend_request.json:

{
  "firstName": "<your-new-first-name>",
  "unsubscribed": true
}

Then run:

bash -c 'curl -s -X PATCH "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Delete Contact

bash -c 'curl -s -X DELETE "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Domains

List Domains

bash -c 'curl -s "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_API_KEY"'

Retrieve Domain

bash -c 'curl -s "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Create Domain

Write to /tmp/resend_request.json:

{
  "name": "<your-domain-name>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Verify Domain

bash -c 'curl -s -X POST "https://api.resend.com/domains/<your-domain-id>/verify" --header "Authorization: Bearer $RESEND_API_KEY"'

Delete Domain

bash -c 'curl -s -X DELETE "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

API Keys

List API Keys

bash -c 'curl -s "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY"'

Create API Key

Write to /tmp/resend_request.json:

{
  "name": "<your-key-name>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Create API Key with Permissions

Write to /tmp/resend_request.json:

{
  "name": "<your-key-name>",
  "permission": "sending_access"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Delete API Key

bash -c 'curl -s -X DELETE "https://api.resend.com/api-keys/<your-api-key-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Email Parameters Reference

Response Codes

Guidelines

1. Rate Limits: Default is 2 requests per second; implement backoff for 429 errors
2. Sender Domain: Use verified domains for production; onboarding@resend.dev for testing
3. Batch Emails: Use /emails/batch for sending to multiple recipients efficiently
4. Idempotency: Use Idempotency-Key header to prevent duplicate sends
5. Scheduling: Use natural language (in 1 hour) or ISO 8601 format for scheduledAt

API Reference

• Documentation: https://resend.com/docs/api-reference/introduction
• Dashboard: https://resend.com/overview
• API Keys: https://resend.com/api-keys
• Domains: https://resend.com/domains