🤖 Gmail Auto-Reply Bot with Python

Your inbox works while you sleep. Intelligent email responses powered by keyword detection and Python automation.

🎯 Overview

Tired of manually responding to repetitive emails? This Python-based auto-reply system monitors your Gmail inbox 24/7 and sends intelligent, context-aware responses based on email content. Perfect for handling support requests, meeting inquiries, and common questions while you focus on what matters.

✨ Features

🎨 Smart Response System

Keyword Detection - Automatically categorizes emails by content
Context-Aware Replies - Sends appropriate responses based on email type
6 Built-in Templates - Meeting requests, support, pricing, urgent matters, billing, and job applications
Customizable Rules - Add your own keywords and response templates

🔄 Automation & Safety

Real-time Monitoring - Checks inbox every 60 seconds (configurable)
Duplicate Prevention - Never sends the same reply twice
Self-Reply Protection - Won't respond to your own emails
Auto-Mark Read - Keeps your inbox organized
Date Filtering - Only processes emails from today onwards (customizable)

⚙️ Technical Features

IMAP/SMTP integration with Gmail
App password authentication (secure)
Thread-safe reply handling
JSON-based rule configuration
Comprehensive error handling

📥 Installation

Prerequisites

Python 3.7 or higher
Gmail account with IMAP enabled
Gmail App Password (not your regular password)

Quick Setup

1. Clone or Download

# Download the files:
- email_auto_reply.py
- reply_rules.json

📧 email_auto_reply 📄 reply_rules

2. Install Dependencies

pip install imaplib-utf7

That's it! No external packages needed - uses Python standard library.

🚀 Quick Start (5 Minutes)

Step 1: Get Gmail App Password

Go to https://myaccount.google.com/apppasswords
Sign in to your Google Account
Create a new App Password:
- Select "Mail" as the app
- Select your device
- Click "Generate"
Copy the 16-character password

Example: abcd efgh ijkl mnop

Step 2: Configure Your Credentials

Open email_auto_reply.py and update these lines:

# Find these lines at the bottom of the file:
EMAIL = "your.email@gmail.com"  # ← Change this
APP_PASSWORD = "your-app-password"  # ← Paste your app password

Replace with your actual credentials:

EMAIL = "john.doe@gmail.com"
APP_PASSWORD = "abcd efgh ijkl mnop"

Step 3: Run the Bot

python3 email_auto_reply.py

You should see:

Email Auto-Reply System Started
Monitoring: john.doe@gmail.com
Check interval: 60 seconds
Press Ctrl+C to stop

[2025-10-22 10:30:00] Checking for new emails...
No unread emails found from 22-Oct-2025 onwards
Waiting 60 seconds until next check...

Step 4: Test It!

Send a test email to yourself:

From another email account, send an email to your Gmail
Include keywords like "urgent" or "meeting" in the subject or body
Wait up to 60 seconds
Check if you received an auto-reply!

📋 Default Auto-Reply Rules

The system recognizes these keywords and sends appropriate responses:

1. 📅 Meeting/Scheduling

Keywords: meeting, schedule, appointment, calendar

Reply:

Hello,

Thank you for your email regarding scheduling. I've received your 
message and will review my calendar to find a suitable time.

I'll get back to you within 24 hours with my availability.

Best regards

2. 🚨 Urgent Matters

Keywords: urgent, asap, emergency, immediate

Reply:

Hello,

I've received your urgent message and it has been flagged for 
priority attention.

I will respond as soon as possible.

Best regards

3. 💰 Pricing Inquiries

Keywords: quote, pricing, price, cost, estimate

Reply:

Hello,

Thank you for your inquiry about pricing. I've received your 
request for a quote.

I will prepare the information and send you a detailed response 
within 2 business days.

Best regards

4. 🛠️ Support Requests

Keywords: support, help, issue, problem, bug

Reply:

Hello,

Thank you for contacting support. Your message has been received 
and logged.

Our support team will review your issue and respond within 24-48 hours.

Best regards

5. 💳 Billing/Invoice

Keywords: invoice, payment, bill, receipt

Reply:

Hello,

Thank you for your message regarding billing. I've received your inquiry.

Our accounting team will review this and respond within 2 business days.

Best regards

6. 👔 Job Applications

Keywords: application, job, position, resume, cv

Reply:

Hello,

Thank you for your interest and for submitting your application. 
We have received your materials.

Our team will review your application and contact you if your 
qualifications match our current needs.

Best regards

🎨 Customization

Method 1: Edit the Python File

Add custom rules directly in email_auto_reply.py:

# Find the load_default_rules() function and add:
{
    "keywords": ["refund", "return"],
    "reply_template": """Hello,

Thank you for your refund request. Our team will process this 
within 5 business days.

Best regards"""
}

Method 2: Use JSON Configuration

Edit reply_rules.json:

[
  {
    "keywords": ["demo", "trial", "free trial"],
    "reply_template": "Hello,\n\nThank you for your interest in our demo!\n\nI'll send you access details within 24 hours.\n\nBest regards"
  }
]

Load custom rules:

auto_reply = EmailAutoReply(EMAIL, APP_PASSWORD)
auto_reply.load_rules("reply_rules.json")

Method 3: Add Rules Programmatically

auto_reply = EmailAutoReply(EMAIL, APP_PASSWORD)

auto_reply.add_custom_rule(
    keywords=["partnership", "collaboration", "sponsor"],
    reply_template="Thank you for reaching out about partnership opportunities..."
)

# Save rules for next time
auto_reply.save_rules("my_custom_rules.json")

⚙️ Advanced Configuration

Custom Date Range

Process emails from a specific date:

from datetime import date

# Start from October 15, 2025
custom_date = date(2025, 10, 15)
auto_reply = EmailAutoReply(EMAIL, APP_PASSWORD, start_date=custom_date)

Change Check Interval

# Check every 30 seconds (instead of 60)
auto_reply.run_continuous(check_interval=30)

# Check every 5 minutes
auto_reply.run_continuous(check_interval=300)

Process Once (No Continuous Loop)

auto_reply = EmailAutoReply(EMAIL, APP_PASSWORD)
auto_reply.process_unread_emails()  # Process once and exit

🎯 Use Cases

For Freelancers

Auto-respond to client inquiries
Handle meeting requests automatically
Send instant pricing confirmations
Manage support tickets

For Small Businesses

24/7 customer support acknowledgment
Handle job applications
Manage billing inquiries
Schedule meetings efficiently

For Developers

GitHub issue notifications
Support ticket automation
Bug report acknowledgments
API inquiry handling

For Job Seekers

Auto-respond to recruiter emails
Acknowledge interview invitations
Handle follow-up inquiries
Manage application confirmations

🔒 Security & Privacy

✅ Best Practices

1. Use App Passwords (Never Regular Password)

# ✅ CORRECT
APP_PASSWORD = "abcd efgh ijkl mnop"  # App password

# ❌ WRONG - Never use your regular password!
APP_PASSWORD = "myGmailPassword123"

2. Keep Credentials Secret

# Store in environment variables (production)
import os
EMAIL = os.getenv('GMAIL_ADDRESS')
APP_PASSWORD = os.getenv('GMAIL_APP_PASSWORD')

3. Never Commit Credentials to Git

# Add to .gitignore
echo "config.py" >> .gitignore
echo "*.env" >> .gitignore

4. Test Before Production

Test with a secondary Gmail account first
Review all auto-replies before enabling 24/7
Monitor the first few hours closely

🔧 Troubleshooting

Problem: "Authentication failed"

❌ Failed to connect to IMAP: [AUTHENTICATIONFAILED]

Solutions:

Double-check your email and app password
Make sure you're using an App Password, not your regular password
Verify IMAP is enabled in Gmail settings

Problem: "No unread emails found"

No unread emails found from 22-Oct-2025 onwards

Solutions:

The system only processes unread emails
Try sending a new test email
Or mark an existing email as unread
Check if your start date is correct

Problem: Not receiving replies

Solutions:

Check your spam folder
Wait for the full check interval (60 seconds)
Look for error messages in the terminal
Verify the keyword matching is working

Problem: "Connection timeout"

Solutions:

Check your internet connection
Verify Gmail servers are accessible
Try increasing timeout in the code
Check firewall settings

💡 Pro Tips

1. Start with Whitelist Mode

Only respond to specific senders:

def process_unread_emails(self):
    # Add this check after getting sender_email
    allowed_senders = ["client@example.com", "boss@company.com"]
    if sender_email not in allowed_senders:
        continue

2. Add Time Delays

Avoid looking too robotic:

import random
time.sleep(random.randint(30, 120))  # Wait 30-120 seconds before replying

3. Log Everything

Track all auto-replies:

import logging
logging.basicConfig(filename='auto_replies.log', level=logging.INFO)
logging.info(f"Replied to {sender_email} at {timestamp}")

4. Set Business Hours

Only send replies during work hours:

from datetime import datetime

current_hour = datetime.now().hour
if 9 <= current_hour <= 17:  # 9 AM to 5 PM
    self.send_reply(...)

5. Add Rate Limiting

Prevent spam:

self.reply_count = {}

def send_reply(self, to_address, ...):
    # Max 3 replies per sender per day
    if self.reply_count.get(to_address, 0) >= 3:
        return False
    
    # Send reply...
    self.reply_count[to_address] = self.reply_count.get(to_address, 0) + 1

📊 How It Works

System Architecture

┌─────────────┐
│   Gmail     │
│   Inbox     │
└──────┬──────┘
       │
       │ IMAP Connection
       │
┌──────▼──────────────────────┐
│  Python Auto-Reply Bot      │
│                             │
│  1. Connect to IMAP         │
│  2. Fetch unread emails     │
│  3. Analyze content         │
│  4. Match keywords          │
│  5. Generate reply          │
│  6. Send via SMTP           │
│  7. Mark as read            │
└──────┬──────────────────────┘
       │
       │ SMTP Send
       │
┌──────▼──────┐
│  Recipient  │
│  Inbox      │
└─────────────┘

Code Flow

while True:
    # 1. Connect to Gmail
    mail = imaplib.IMAP4_SSL("imap.gmail.com")
    mail.login(email, password)
    
    # 2. Get unread emails
    mail.select('INBOX')
    status, messages = mail.search(None, 'UNSEEN')
    
    # 3. Process each email
    for email_id in messages:
        msg = fetch_email(email_id)
        
        # 4. Analyze content
        subject = msg['Subject']
        body = get_body(msg)
        
        # 5. Find matching rule
        reply = analyze_message(subject, body)
        
        # 6. Send reply
        send_reply(sender, subject, reply)
        
        # 7. Mark as read
        mark_read(email_id)
    
    # 8. Wait and repeat
    time.sleep(60)

🚨 Important Notes

What This Bot Does:

✅ Monitors Gmail inbox continuously
✅ Sends automatic replies to unread emails
✅ Categorizes emails by keywords
✅ Marks emails as read after replying
✅ Prevents duplicate replies

What This Bot Doesn't Do:

❌ Won't reply to emails from yourself
❌ Won't reply to already-read emails
❌ Won't reply twice to the same email
❌ Won't process emails older than start date
❌ Won't send replies if sending fails

Safety Checks:

# Self-reply protection
if sender_email == self.email_address:
    continue

# Duplicate prevention
if email_id in self.processed_emails:
    continue

# Error handling
try:
    send_reply(...)
except Exception as e:
    log_error(e)

🔄 Deployment Options

Option 1: Run Locally (Development)

python3 email_auto_reply.py

Pros: Easy, immediate testing Cons: Stops when computer sleeps

Option 2: Background Process (Linux/Mac)

nohup python3 email_auto_reply.py > output.log 2>&1 &

Pros: Runs in background Cons: Still requires local machine

Option 3: Cloud Server (24/7)

On AWS EC2, DigitalOcean, or similar:

# 1. Upload script to server
scp email_auto_reply.py user@server:/home/user/

# 2. SSH into server
ssh user@server

# 3. Run with screen/tmux
screen -S email-bot
python3 email_auto_reply.py

# 4. Detach with Ctrl+A then D

Option 4: Systemd Service (Linux)

Create /etc/systemd/system/email-autoreply.service:

[Unit]
Description=Gmail Auto-Reply Bot
After=network.target

[Service]
Type=simple
User=youruser
WorkingDirectory=/home/youruser/email-bot
ExecStart=/usr/bin/python3 email_auto_reply.py
Restart=always

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable email-autoreply
sudo systemctl start email-autoreply
sudo systemctl status email-autoreply

📚 Code Structure

email-auto-reply/
├── email_auto_reply.py      # Main bot script
├── reply_rules.json          # Custom reply rules
├── QUICKSTART.md             # Quick setup guide
├── README.md                 # Full documentation
└── .gitignore               # Exclude credentials

Key Classes & Functions:

class EmailAutoReply:
    def __init__()              # Initialize with credentials
    def connect_imap()          # Connect to Gmail
    def process_unread_emails() # Process inbox
    def analyze_message()       # Find matching rule
    def send_reply()            # Send auto-reply
    def run_continuous()        # Run 24/7

🎓 Learning Resources

Understanding IMAP

Python Email Libraries

Security

🚀 Next Steps & Enhancements

Easy Additions:

[ ] Add HTML email templates
[ ] Include attachments in replies
[ ] Support multiple Gmail accounts
[ ] Add email signature with logo

Advanced Features:

[ ] Natural Language Processing (NLP) for better categorization
[ ] Machine learning to improve responses over time
[ ] Integration with CRM systems
[ ] Webhook notifications to Slack/Discord
[ ] Analytics dashboard (emails processed, response times)

Enterprise Features:

[ ] Multi-user support
[ ] Role-based reply rules
[ ] API endpoint for external triggers
[ ] Database integration for logging
[ ] Admin dashboard

⚖️ License

MIT License - feel free to use, modify, and distribute!

🙏 Acknowledgments

Built with Python standard library
Powered by Gmail IMAP/SMTP
Inspired by the need for efficient email management
Community-driven feature requests

📬 Support & Feedback

Found a bug? Open an issue Want a feature? Submit a pull request Need help? Check the troubleshooting guide

🎯 Quick Recap

Setup Time: 5 minutes Difficulty: Beginner-friendly Dependencies: Python standard library Cost: Free (just need Gmail) Maintenance: Set it and forget it

Ready to automate your inbox?

python3 email_auto_reply.py

No sign-up. No credit card. Just results. 📧

⭐ Star this project if it helped you save time!

Made with ❤️ by Thiekshana for busy professionals worldwide

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