Email Newsletter System with SendGrid, Google Sheets & Freemium Rate Limiting
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Gilbert Onyebuchi
Description
A complete email campaign automation system featuring dual-mode access control (Demo/Pro), usage tracking, and professional email delivery. Perfect for SaaS products, marketing agencies, or anyone building newsletter tools with freemium models.
WHAT IT DOES
This workflow manages email newsletter campaigns with built-in rate limiting for free users and unlimited access for premium users. It automatically tracks daily usage, manages user data in Google Sheets, delivers emails via SendGrid, and sends real-time notifications through Telegram.
KEY FEATURES
Dual-Mode System: Demo mode (5 emails/day) and Pro mode (unlimited)
Smart Rate Limiting: Automatic daily counter reset
User Management: Automatic new user registration and tracking
Google Sheets Integration: Stores user data, send counts, and usage history
Professional Email Delivery: SendGrid integration for reliable sending
Real-Time Monitoring: Telegram notifications for every send
Ready-to-Use Templates: 4 professional email designs included (Modern, Professional, Promotional, Newsletter)
Live Preview: See exactly how emails look before sending
HTML Export: Copy email HTML for use in any platform
HOW IT WORKS
User accesses the Email Newsletter Builder web form
Designs email using one of 4 professional templates
Chooses Demo or Pro mode
Webhook receives the email data and configuration
Workflow checks mode (Demo/Pro)
For Demo mode:
Queries Google Sheets for user email
Checks if user exists and validates daily limit (<5 sends)
If new user: Creates database entry
If existing user + under limit: Increments counter
If limit reached: Returns error message
For Pro mode: Sends immediately without limits
SendGrid delivers the email
Google Sheets updates with new send count and timestamp
Telegram notification sent to admin
Success/error response returned to user
SETUP REQUIREMENTS
Google Sheets account (free)
SendGrid account (free tier: 100 emails/day)
Telegram account + bot (free)
n8n instance (self-hosted or cloud)
SUPPORT & FEEDBACK
Questions or issues? Connect with me on LinkedIn
Want to see it in action? Try the live demo: Click here
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