resend

Troubleshooting

If requests fail, run zero doctor check-connector --env-name RESEND_TOKEN or zero doctor check-connector --url https://api.resend.com/emails --method POST

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 $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 $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 $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 $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 $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 $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 $RESEND_TOKEN"

List Sent Emails

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

Cancel Scheduled Email

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

List Contacts

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

List Contacts with Pagination

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

Domains

List Domains

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

Retrieve Domain

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

Delete Domain

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

API Keys

List API Keys

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

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 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