Send Email from an AI Agent: Outbound Email API Guide

Sending email from an AI agent should be simple. AgentMailr exposes a REST API that lets any agent send an email with a single HTTP POST.

Send a Plain Email

POST /v1/inboxes/{inbox_id}/send
X-API-Key: ak_your_key
Content-Type: application/json

{
  "to": "user@example.com",
  "subject": "Task Complete",
  "text": "I finished the research you requested. Here is a summary...",
  "html": "<p>I finished the research...</p>"
}

Reply to an Email

POST /v1/inboxes/{inbox_id}/reply
{
  "email_id": "eml_abc123",
  "text": "Thanks for your reply. Here is the next step..."
}

The reply automatically sets In-Reply-To and References headers so it appears in the same thread for the recipient.

Forward an Email

POST /v1/inboxes/{inbox_id}/forward
{
  "email_id": "eml_abc123",
  "to": "manager@company.com",
  "note": "FYI — this arrived in the agent inbox this morning."
}

Bulk Send

POST /v1/send/bulk
{
  "from": "newsletter@agents.yourcompany.com",
  "subject": "Weekly Update",
  "text": "This week's highlights...",
  "recipients": [
    { "email": "alice@example.com", "name": "Alice" },
    { "email": "bob@example.com", "name": "Bob" }
  ]
}

Send up to 100 emails in a single batch request.

Outbound Providers

AgentMailr uses Resend and AWS SES for outbound delivery. Both have excellent deliverability. Emails are stored in the inbox's sent folder so your agent can retrieve them later.