Send Email

Send an Email

Use this skill when an AI agent needs to send an email - a reply, a notification, a form submission, or outbound agent-to-human communication.

When to use

• Agent needs to reply to an email it received
• Agent needs to initiate outbound contact (notify a user, file a form)
• Agent needs to forward an email

Prerequisites

• A Lumbox inbox ID (see the create-lumbox-inbox skill)
• LUMBOX_API_KEY environment variable set
• Recipient email address

Steps

1. Call the send endpoint:

   curl -X POST "https://api.lumbox.co/v1/inboxes/$INBOX_ID/send" \
     -H "X-API-Key: $LUMBOX_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "to": "recipient@example.com",
       "subject": "Hello from an AI agent",
       "text": "Plain text body.",
       "html": "<p>HTML body.</p>"
     }'
   

2. Read the response. You get a message ID that identifies this email for future threading:

   {
     "id": "eml_7y3c...",
     "message_id": "<abc123@lumbox.co>",
     "sent_at": "2026-04-18T10:35:00.000Z"
   }
   

3. For replies, use the reply endpoint instead - it sets In-Reply-To and References headers correctly so the email threads in the recipient's client:

   curl -X POST "https://api.lumbox.co/v1/inboxes/$INBOX_ID/reply" \
     -H "X-API-Key: $LUMBOX_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "reply_to_email_id": "eml_of_original",
       "text": "Thanks for the OTP."
     }'
   

Tips

• Sending uses AWS SES under the hood - deliverability is high.
• For bulk sends (up to 100 recipients at once), use /v1/send/bulk.
• Attachments: include a attachments array with filename and base64 content.
• To forward: use /v1/inboxes/:id/forward with the email ID and new recipient.

Related skills

• create-lumbox-inbox - provision the sending inbox
• wait-for-otp - receive the reply if the recipient sends one back