Resend Email API

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

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

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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

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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.

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Emails

Send Email

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-email}"], "subject": "{subject}", "html": "<p>{html-content}</p>"}'"'"'' | jq .

Send Email with Plain Text

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-email}"], "subject": "{subject}", "text": "{plain-text-content}"}'"'"'' | jq .

Send Email with CC/BCC

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-email}"], "cc": ["{cc-email}"], "bcc": ["{bcc-email}"], "subject": "{subject}", "html": "<p>{html-content}</p>"}'"'"'' | jq .

Send Email with Reply-To

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-email}"], "replyTo": "{reply-to-email}", "subject": "{subject}", "html": "<p>{html-content}</p>"}'"'"'' | jq .

Send Scheduled Email

Schedule email using natural language or ISO 8601 format:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-email}"], "subject": "{subject}", "html": "<p>{html-content}</p>", "scheduledAt": "in 1 hour"}'"'"'' | jq .

Send Batch Emails

Send up to 100 emails in a single request:

bash -c 'curl -s -X POST "https://api.resend.com/emails/batch" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'[{"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-1}"], "subject": "Hello 1", "html": "<p>Email 1</p>"}, {"from": "Acme <onboarding@resend.dev>", "to": ["{recipient-2}"], "subject": "Hello 2", "html": "<p>Email 2</p>"}]'"'"'' | jq .

Retrieve Email

bash -c 'curl -s "https://api.resend.com/emails/{email-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

List Sent Emails

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

Cancel Scheduled Email

bash -c 'curl -s -X POST "https://api.resend.com/emails/{email-id}/cancel" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

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Contacts

Create Contact

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"email": "{contact-email}", "firstName": "{first-name}", "lastName": "{last-name}", "unsubscribed": false}'"'"'' | jq .

Create Contact with Custom Properties

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"email": "{contact-email}", "firstName": "{first-name}", "lastName": "{last-name}", "properties": {"company": "{company-name}", "role": "{role}"}}'"'"'' | jq .

Retrieve Contact

bash -c 'curl -s "https://api.resend.com/contacts/{contact-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

List Contacts

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

List Contacts with Pagination

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

Update Contact

bash -c 'curl -s -X PATCH "https://api.resend.com/contacts/{contact-id}" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"firstName": "{new-first-name}", "unsubscribed": true}'"'"'' | jq .

Delete Contact

bash -c 'curl -s -X DELETE "https://api.resend.com/contacts/{contact-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

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Domains

List Domains

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

Retrieve Domain

bash -c 'curl -s "https://api.resend.com/domains/{domain-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

Create Domain

bash -c 'curl -s -X POST "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"name": "{domain-name}"}'"'"'' | jq .

Verify Domain

bash -c 'curl -s -X POST "https://api.resend.com/domains/{domain-id}/verify" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

Delete Domain

bash -c 'curl -s -X DELETE "https://api.resend.com/domains/{domain-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

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API Keys

List API Keys

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

Create API Key

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"name": "{key-name}"}'"'"'' | jq .

Create API Key with Permissions

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d '"'"'{"name": "{key-name}", "permission": "sending_access"}'"'"'' | jq .

Delete API Key

bash -c 'curl -s -X DELETE "https://api.resend.com/api-keys/{api-key-id}" --header "Authorization: Bearer $RESEND_API_KEY"' | jq .

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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
replyTo	string	Reply-to address
scheduledAt	string	Schedule time (ISO 8601 or natural language)
tags	array	Custom tags for tracking
attachments	array	File attachments (max 40MB total)

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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

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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

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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