Email Notification System
Overview
A robust email notification system for sending transactional emails (password resets, receipts, account updates) with template management, queuing for reliability, and delivery tracking. The system ensures emails are sent promptly, handles failures gracefully, and provides admins with visibility into email delivery.
User Stories
- As a user, I want to receive important notifications via email, so that I stay informed about account activity
- As a user, I want emails to be well-formatted and on-brand, so that they feel professional
- As a developer, I want to use email templates, so that I can easily add new notification types
- As an admin, I want to track email delivery status, so that I can troubleshoot issues
- As a user, I want to unsubscribe from marketing emails, so that I control what I receive
Acceptance Criteria
- [ ] System sends emails for: signup, password reset, payment receipt, subscription renewal
- [ ] Emails use HTML templates with responsive design
- [ ] Templates include dynamic variables (user name, reset link, invoice details)
- [ ] Emails sent within 2 minutes of triggering event
- [ ] Failed emails automatically retry 3 times with exponential backoff
- [ ] Delivery status logged (sent, delivered, bounced, failed)
- [ ] Unsubscribe link included in marketing emails (not transactional)
- [ ] Admin dashboard shows email stats (sent, opened, clicked, failed)
Technical Requirements
- Use transactional email service (SendGrid, Postmark, AWS SES)
- Implement email queue (Redis, Bull, or database-backed)
- Create reusable email templates with variables
- Store email logs in database (recipient, type, status, timestamp)
- Handle webhook callbacks for delivery events
- Implement rate limiting to respect provider limits
- Use environment variables for API keys
- Test emails in development with email preview tool (Mailtrap, Ethereal)
Edge Cases
- Email service is down → Queue emails, retry when service recovers
- Invalid email address → Mark as failed, log error, don't retry
- Bounce or spam complaint → Mark user email as invalid, stop sending
- User changes email before verification email delivered → Invalidate old email, send to new
- High volume of emails (1000+ in short time) → Queue processes in batches to respect rate limits
Out of Scope
- In-app notifications (push, toast)
- SMS notifications
- Email marketing campaigns (newsletters)
- A/B testing email content
- Advanced analytics (open rate tracking, click heatmaps)