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Automated Professional Email Reply Generator API

Email API

Automated Professional Email Reply Generator API

Context-aware email reply generation API grounded in business knowledge bases, custom rules, and tone controls.

POST https://rsflowhub.com/api/v1/ai/email-reply

2 credits per call
X-API-Key header
JSON in, JSON out

Try it in the playground API reference

POST /api/v1/ai/email-reply

{
    "email_text": "Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.",
    "sender_name": "John Doe",
    "recipient_name": "Support Team",
    "knowledge_base": [
        "Refunds are only issued if requested within 14 days of the charge.",
        "Standard response time is 24 hours."
    ],
    "rules": [
        "Never promise a refund if you are unsure.",
        "Be empathetic but firm.",
        "If the user threatens a chargeback, escalate to a human."
    ],
    "tone": "professional"
}

200 OK response.json

{
    "result": {
        "reply_text": "Hi there, thanks for flagging this. I can see the duplicate charge on your March invoice and have started a refund for the second payment. You should see it within 5-7 business days.",
        "confidence_score": 0.91,
        "requires_human_escalation": false,
        "escalation_reason": null,
        "triggered_actions": []
    }
}

Definition

What is the Automated Professional Email Reply Generator API?

Automated Professional Email Reply Generator API is a REST API on RSFlowHub for web, mobile and AI agent applications. Send a JSON request to POST /api/v1/ai/email-reply with your API key; RSFlowHub runs it on a tuned AI model, falls back to a backup provider if needed, and returns a structured JSON result, usually within 1 to 3 seconds.

Try it without code or signup: Free email reply generator

Category: Email
Endpoint: POST /api/v1/ai/email-reply
Authentication: X-API-Key header
Price: 2 credits per call
Rate limit: 10 to 120 requests / minute by plan
Typical response: 1 to 3 seconds
Format: JSON, UTF-8

Request parameters

Send these fields as a JSON body. An invalid or missing field returns a 422 error that names the field.

Field	Type	Required	Description
`email_text`	string	Required	The raw text of the incoming email (Max: 20,000 characters).
`context`	string	Optional	Optional general context or instructions for drafting the reply.
`tone`	string	Optional	Tone of the reply (e.g., "professional", "empathetic", "casual").
`sender_name`	string	Optional	Name of the person who sent the email.
`recipient_name`	string	Optional	Name of your team or agent.
`knowledge_base`	array of strings	Optional	Array of factual sentences the AI must use to answer questions (e.g., ["Business hours are 9-5", "No refunds after 30 days"]).
`rules`	array of strings	Optional	Strict rules for the AI to follow (e.g., ["Never promise a refund", "Always escalate chargebacks"]).

Code examples

Copy, replace rfh_your_api_key with your key and run. Prefer a client library? See the official SDKs.

request.sh

curl -X POST "https://rsflowhub.com/api/v1/ai/email-reply" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: rfh_your_api_key" \
  -d '{"email_text":"Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.","sender_name":"John Doe","recipient_name":"Support Team","knowledge_base":["Refunds are only issued if requested within 14 days of the charge.","Standard response time is 24 hours."],"rules":["Never promise a refund if you are unsure.","Be empathetic but firm.","If the user threatens a chargeback, escalate to a human."],"tone":"professional"}'

client.php

<?php

$client = new \GuzzleHttp\Client();
$response = $client->post('https://rsflowhub.com/api/v1/ai/email-reply', [
    'headers' => [
        'Content-Type' => 'application/json',
        'X-API-Key'    => 'rfh_your_api_key',
    ],
    'json' => array (
      'email_text' => 'Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.',
      'sender_name' => 'John Doe',
      'recipient_name' => 'Support Team',
      'knowledge_base' => 
      array (
        0 => 'Refunds are only issued if requested within 14 days of the charge.',
        1 => 'Standard response time is 24 hours.',
      ),
      'rules' => 
      array (
        0 => 'Never promise a refund if you are unsure.',
        1 => 'Be empathetic but firm.',
        2 => 'If the user threatens a chargeback, escalate to a human.',
      ),
      'tone' => 'professional',
    ),
]);

echo $response->getBody();

client.js

const response = await fetch('https://rsflowhub.com/api/v1/ai/email-reply', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'X-API-Key': 'rfh_your_api_key'
  },
  body: JSON.stringify({"email_text":"Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.","sender_name":"John Doe","recipient_name":"Support Team","knowledge_base":["Refunds are only issued if requested within 14 days of the charge.","Standard response time is 24 hours."],"rules":["Never promise a refund if you are unsure.","Be empathetic but firm.","If the user threatens a chargeback, escalate to a human."],"tone":"professional"})
});

const data = await response.json();
console.log(data);

main.py

import requests

url = "https://rsflowhub.com/api/v1/ai/email-reply"
headers = {
    "Content-Type": "application/json",
    "X-API-Key": "rfh_your_api_key"
}
payload = {"email_text":"Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.","sender_name":"John Doe","recipient_name":"Support Team","knowledge_base":["Refunds are only issued if requested within 14 days of the charge.","Standard response time is 24 hours."],"rules":["Never promise a refund if you are unsure.","Be empathetic but firm.","If the user threatens a chargeback, escalate to a human."],"tone":"professional"}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

Response

Every RSFlowHub endpoint uses the same envelope, so one parser handles all of them. Failed calls are not charged.

response.json

{
    "success": true,
    "request_id": "req_3f9a2c7e-5b1d-4e8a-9c2f-7d6e1a0b4c8d",
    "data": {
        "result": {
            "reply_text": "Hi there, thanks for flagging this. I can see the duplicate charge on your March invoice and have started a refund for the second payment. You should see it within 5-7 business days.",
            "confidence_score": 0.91,
            "requires_human_escalation": false,
            "escalation_reason": null,
            "triggered_actions": []
        }
    },
    "meta": {
        "version": "v1",
        "timestamp": "2026-10-05T09:30:00Z"
    }
}

error.json

{
    "success": false,
    "request_id": "req_8c1d4e2a-7f3b-4a9c",
    "error": {
        "code": "VALIDATION_ERROR",
        "message": "The given data was invalid.",
        "details": {
            "email_text": [
                "This field is required."
            ]
        }
    },
    "meta": {
        "version": "v1",
        "timestamp": "2026-10-05T09:30:00Z"
    }
}

Envelope fields
Field	Type	Meaning
`success`	boolean	true when the call worked, false on any error.
`request_id`	string	Unique id for this call. Quote it when you contact support.
`data.result`	object	The result of this endpoint (see the example).
`error`	object	Only on failure: code, message and details per field.
`meta`	object	API version and server timestamp.

All error codes: Errors reference

Features

Knowledge Base Fact Grounding

Grounds generated responses strictly in your company knowledge base facts, documentation, and refund policies.

Custom Business Rule Enforcement

Enforces strict operational guardrails e.g. "Never promise a refund if unsure" or "Escalate chargeback threats".

Multi-Style & Tone Control

Select between professional, empathetic, firm, concise, or friendly communication tones.

Sender & Recipient Personalization

Formats professional email greetings, recipient names, sender titles, and signature blocks automatically.

Use cases

How teams use the Automated Professional Email Reply Generator API in production.

Customer Support

Helpdesk Support Ticket Auto-Drafting

Generate instant professional draft replies for support agents answering billing and account inquiries.

Input: Hi, I was charged $49 but I cancelled my account yesterday. Please refund me immediately.
Output: Dear John,\n\nThank you for contacting RSFlowHub Support. I understand you were charged after requesting cancellation. Our team is processing your $49 refund, which will post in 3-5 business days.\n\nBest regards,\nSupport Team

Saves support representatives 3+ minutes per ticket response.

Corporate Email

Intelligent Out-of-Office & Auto-Responders

Generate context-aware out-of-office replies providing targeted contact links depending on sender query.

Input: Hi, I need urgent access to the Q3 financial report.
Output: Hi,\n\nI am currently out of the office until Monday. For urgent financial report inquiries, please contact finance@company.com.

Provides instant guidance even when staff is offline.

E-Commerce

E-Commerce Refund Policy Automated Response

Automatically respond to buyer refund inquiries following exact store 14-day policy rules.

Input: Can I return an item I bought 10 days ago?
Output: Hello,\n\nYes! We accept returns within 14 days of purchase. Please visit our Returns Portal at example.com/returns to print your shipping label.

Drafts accurate answers to order-status emails for one-click sending.

Automated Professional Email Reply Generator API vs building it yourself

The same job done three ways.

Topic	RSFlowHub API	Raw LLM prompts	Rules / regex
Output	Validated JSON fields	Free text you have to parse	Fixed patterns only
Setup	One POST request, no prompts	Write and maintain prompts and parsing	Write and maintain rule lists
Provider outage	Automatic fallback to a backup model	You build retries and a second vendor	Not applicable
Pricing	2 credits per call, failed calls free	Per token, per vendor	Your own servers and upkeep
Understands context	Yes, AI model	Yes, AI model	No, keywords only

Frequently asked questions

How does knowledge base grounding prevent AI hallucinations?

The generation engine strictly constrains facts to the provided knowledge_base array, preventing invented policies or incorrect promises.

Can I specify strict business rules for email generation?

Yes! Passing operational rules (e.g. "Never promise a refund without manager review") forces the engine to comply with internal SOPs.

How does the API format salutations and sign-offs?

The API automatically uses recipient_name for formal greetings (e.g., "Dear John,") and sender_name for professional closing sign-offs.

How fast is the Email Reply Generator API?

Email Reply Generator requests usually complete in 1 to 3 seconds, depending on input length and the AI model. Identical repeat requests are served from cache and return faster.

How many credits are deducted per request?

Standard Email Reply Generator API calls consume 2 base credits per request.

Start using the Automated Professional Email Reply Generator API

Free plan with 100 credits/month + 1,000 bonus credits when you sign in before 23 Nov. Test it in the playground first, no code needed.

Get a free API key Try it now