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

Important: When using $RESEND_TOKEN in commands that contain a pipe (|), always wrap the curl command in bash -c '...' to avoid silent variable clearing — a known Claude Code issue.

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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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>"],
  "reply_to": "<your-reply-to-email>",
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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>",
  "scheduled_at": "in 1 hour"
}

Then run:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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:

curl -s -X POST "https://api.resend.com/emails/batch" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --header "Content-Type: application/json" -d @/tmp/resend_request.json

Retrieve Email

curl -s "https://api.resend.com/emails/<your-email-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

List Sent Emails

curl -s "https://api.resend.com/emails" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Cancel Scheduled Email

curl -s -X POST "https://api.resend.com/emails/<your-email-id>/cancel" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Contacts

Create Contact

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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>",
  "first_name": "<your-first-name>",
  "last_name": "<your-last-name>",
  "properties": {
    "company": "<your-company-name>",
    "role": "<your-role>"
  }
}

Then run:

curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --header "Content-Type: application/json" -d @/tmp/resend_request.json

Retrieve Contact

curl -s "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

List Contacts

curl -s "https://api.resend.com/contacts" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

List Contacts with Pagination

curl -s "https://api.resend.com/contacts?limit=50" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Update Contact

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X PATCH "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --header "Content-Type: application/json" -d @/tmp/resend_request.json

Delete Contact

curl -s -X DELETE "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Domains

List Domains

curl -s "https://api.resend.com/domains" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Retrieve Domain

curl -s "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Create Domain

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X POST "https://api.resend.com/domains" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --header "Content-Type: application/json" -d @/tmp/resend_request.json

Verify Domain

curl -s -X POST "https://api.resend.com/domains/<your-domain-id>/verify" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Delete Domain

curl -s -X DELETE "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

API Keys

List API Keys

curl -s "https://api.resend.com/api-keys" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Create API Key

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --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:

curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $(printenv RESEND_TOKEN)" --header "Content-Type: application/json" -d @/tmp/resend_request.json

Delete API Key

curl -s -X DELETE "https://api.resend.com/api-keys/<your-api-key-id>" --header "Authorization: Bearer $(printenv RESEND_TOKEN)"

Email Parameters Reference

Parameter	Type	Description
`from`	string	Sender email (required). Format: `"Name <email@domain.com>"`
`to`	string[]	Recipients (required). Max 50 addresses
`subject`	string	Email subject (required)
`html`	string	HTML content
`text`	string	Plain text content
`cc`	string[]	CC recipients
`bcc`	string[]	BCC recipients
`reply_to`	string	Reply-to address
`scheduled_at`	string	Schedule time (ISO 8601 or natural language)
`tags`	array	Custom tags for tracking
`attachments`	array	File attachments (max 40MB total)

Response Codes

Status	Description
`200`	Success
`400`	Invalid parameters
`401`	Missing API key
`403`	Invalid API key
`404`	Resource not found
`429`	Rate limit exceeded (2 req/sec)
`5xx`	Server error

Guidelines

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

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