twilio-email-send

Overview

Agent safety: Always confirm recipients, subject, and content with the user before sending. Email is irreversible once delivered. Never send email autonomously without explicit user approval — especially for batch sends to multiple recipients.

Twilio Email is a separate product from SendGrid. Both send email, but they use different APIs, credentials, templating languages, and endpoints. If you have a SendGrid API key (SG.-prefix), use twilio-sendgrid-email-send instead.

	Twilio Email (this skill)	SendGrid
Base URL	https://comms.twilio.com/v1/emails	https://api.sendgrid.com/v3/mail/send
Auth	Twilio Account SID + Auth Token (or API Key SID + Secret)	SendGrid API key (SG.-prefix)
Templating	Liquid ({{variable}})	Handlebars ({{variable}})
Max recipients/request	10,000	1,000
Max message size	10MB (including attachments)	30MB
Status tracking	Operation resource (poll operationLocation)	Event Webhooks (async POST)
Console	console.twilio.com	app.sendgrid.com

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Prerequisites

• A Twilio account — see twilio-account-setup for signup and credentials
• A Verified Sender: an approved domain identity configured in the Twilio console that must match the from address domain
• Compliance with regional anti-spam regulations (CAN-SPAM, GDPR)

For a complete setup guide, see the Email Onboarding guide in the Twilio console.

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Authentication

The API uses Basic Authentication with either:

• Account SID + Auth Token
• API Key SID + API Key Secret

These are standard Twilio credentials — the same ones used for SMS, Voice, and other Twilio APIs.

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Send a Simple Email

POST https://comms.twilio.com/v1/Emails

The endpoint is asynchronous — it returns 202 Accepted with an operationId, not a delivery confirmation.

curl -X POST "https://comms.twilio.com/v1/Emails" \
  --header "Content-Type: application/json" \
  --data '{
    "from": {
      "address": "[email protected]",
      "name": "Support Team"
    },
    "to": [
      {
        "address": "[email protected]",
        "name": "John Doe"
      }
    ],
    "content": {
      "subject": "Your subject line",
      "html": "<p>Your message content in HTML format.</p>",
      "text": "Your message content in plain text."
    }
  }' \
  -u $TWILIO_ACCOUNT_SID:$TWILIO_AUTH_TOKEN

Response (202 Accepted):

{
  "operationId": "...",
  "operationLocation": "https://comms.twilio.com/v1/Emails/Operations/..."
}

Poll operationLocation to track delivery status.

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Batch Sending

Send the same message to multiple recipients in a single request by adding entries to the to array. Maximum 10,000 recipients per request.

{
  "from": {
    "address": "[email protected]",
    "name": "Support Team"
  },
  "to": [
    {
      "address": "[email protected]",
      "name": "John Doe"
    },
    {
      "address": "[email protected]",
      "name": "Jane Smith"
    }
  ],
  "content": {
    "subject": "Your subject line",
    "html": "<p>Your message content in HTML format.</p>",
    "text": "Your message content in plain text."
  }
}

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Liquid Personalization

Use Liquid templating in the content.subject, content.html, and content.text fields. For each variable referenced (e.g. {{firstName}}), provide a matching key in the variables object for every recipient in the to array.

{
  "from": {
    "address": "[email protected]",
    "name": "Support Team"
  },
  "to": [
    {
      "address": "[email protected]",
      "name": "Alice",
      "variables": {"firstName": "Alice", "orderId": "123"}
    },
    {
      "address": "[email protected]",
      "name": "Bob",
      "variables": {"firstName": "Bob", "orderId": "456"}
    }
  ],
  "content": {
    "subject": "Hi {{firstName}}, your order update",
    "html": "<p>Hi {{firstName}}, order #{{orderId}} has shipped.</p>",
    "text": "Hi {{firstName}}, order #{{orderId}} has shipped."
  }
}

Ensure every recipient has all referenced variables defined.

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Operation Tracking

After submitting a send, use the Operation resource to monitor batch status.

1. Submit email via POST /v1/emails — response includes operationId and operationLocation
2. Poll status via GET to the operationLocation URI
3. The operation tracks progress for the entire batch

This is especially important for large recipient lists where processing is not instantaneous.

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Error Codes

Status Code	Description	Action
202	Accepted	Request accepted, Operation created. Poll operationLocation for status.
400	Bad Request	Malformed or ambiguous request content. Check JSON payload.
401	Unauthorized	Verify Account SID and Auth Token / API Key are correct.
429	Too Many Requests	Rate limited. Back off and retry.
500	Internal Server Error	Twilio server-side issue. Retry with backoff.
503	Service Unavailable	Temporarily unavailable. Retry after a short delay.

Validation errors return as many issues as possible in a single response to help debug quickly.

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CANNOT

• Cannot use SendGrid API keys — Twilio Email uses Twilio Account SID + Auth Token or API Key SID + Secret. SG.-prefix keys do not work. Use twilio-sendgrid-email-send for SendGrid.
• Cannot send more than 10,000 recipients per request — Split into multiple requests for larger lists.
• Cannot exceed 10MB per message — Total size including attachments must be under 10MB (smaller than SendGrid's 30MB limit).
• Cannot use Unicode in the from field — Unicode encoding is not supported for sender addresses.
• Cannot use Handlebars templating — Twilio Email uses Liquid, not Handlebars. If you see {{#if}} or {{#each}}, that's Handlebars/SendGrid syntax.
• Cannot get synchronous delivery confirmation — The API is async. 202 Accepted means queued, not delivered. Poll the Operation resource for status.
• Tags total length cannot exceed 10,000 bytes — Combined length of all tags on a request is limited.

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Next Steps

• Account setup and credentials: twilio-account-setup
• SendGrid email (separate product): twilio-sendgrid-email-send
• SMS sending: twilio-sms-send-message