Connecting Email Tools to AI Agents in Dify and Flowise with SadaSend

Why unrestricted email tools in visual agent builders are dangerous

Dify and Flowise have become the leading open-source platforms for building visual LLM applications, RAG pipelines, and autonomous AI agents. As teams move from simple chatbots to autonomous assistants, the natural next step is giving agents the ability to send emails: customer support replies, meeting summaries, lead outreach, and alert dispatches.

However, handing an AI agent an unconstrained email API key (like SendGrid or Mailgun) is an existential security disaster. If the agent is exposed to untrusted user input or an indirect prompt injection attack, the model can be steered to exfiltrate database contents, blast thousands of spam emails, or burn your domain reputation.

The solution is not more prompt engineering—it is cryptographic containment at the credential layer.

The 3 non-negotiable guardrails for agent email

• 1. Scoped Keys: The agent key must only have permission to send, never read logs, create new keys, or delete sending domains.
• 2. Recipient Allowlists: In development and internal testing, restrict the key to your company domain (@yourcompany.com). An agent that is prompt-injected physically cannot dispatch mail to external addresses.
• 3. Human Approval Mode: For high-stakes workflows (billing, refunds, bulk notifications), place the key in Approval Mode. Every send is held in pending_approval until cleared by a human operator in the SadaSend dashboard or via webhook.

Configuring the SadaSend custom tool in Dify

In Dify, you can create a Custom Tool in under 60 seconds using OpenAPI schema definition. Navigate to Tools > Create Custom Tool:

• Name: SadaSend Email Tool

• Schema: Paste the following OpenAPI 3.0 specification snippet:

{
  "openapi": "3.0.0",
  "info": {
    "title": "SadaSend Email Dispatch Tool",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "https://api.sadasend.com/v1"
    }
  ],
  "paths": {
    "/emails": {
      "post": {
        "summary": "Send a transactional email",
        "operationId": "sendEmail",
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "type": "object",
                "properties": {
                  "from": { "type": "string", "description": "Verified sender email" },
                  "to": { "type": "string", "description": "Recipient email address" },
                  "subject": { "type": "string", "description": "Subject line" },
                  "html": { "type": "string", "description": "HTML formatted email body" },
                  "text": { "type": "string", "description": "Plain text fallback" }
                },
                "required": ["from", "to", "subject", "html"]
              }
            }
          }
        },
        "responses": {
          "200": { "description": "Email dispatched successfully" }
        }
      }
    }
  }
}

Flowise custom tool integration with SadaSend

In Flowise, add a Custom Tool node to your Agentflow canvas. Define the tool parameters and provide the JavaScript execution snippet:

// Flowise Custom Tool execution snippet
const fetch = require('node-fetch');

const response = await fetch('https://api.sadasend.com/v1/emails', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${$vars.SADASEND_AGENT_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    from: 'support-agent@yourdomain.com',
    to: $input.recipient,
    subject: $input.subject,
    html: $input.htmlContent,
    text: $input.textContent,
  }),
});

if (!response.ok) {
  const err = await response.json();
  throw new Error(`SadaSend refused dispatch: ${err.message || response.statusText}`);
}

return await response.json();

Safe autonomous customer support agent in action

With SadaSend connected to Dify or Flowise, your AI agent can draft customer responses, verify order details, and queue the email for human approval before sending.