The Real Problem
Email validation in microservices isn't a regex problem. CTOs know this: syntax checks miss deliverability issues, disposable addresses, and catch-all domains. In distributed architectures where Email, Notification, and User Management services operate independently, coordination matters more than pattern matching.
What Works in Practice
Production implementations typically combine frontend validation (React Hook Form, validator.js) with backend services using express-validator or dedicated APIs. The pattern: client-side catches obvious errors, server-side handles deliverability.
External validation services offer quality scores (0.01-0.99 scale) and flag disposable or role-based addresses. Trade-off: added latency versus inline checks. For high-volume transactional systems, the reliability gain justifies the overhead.
The Token Problem
Token-based email verification presents a specific challenge: ensuring uniqueness across distributed services. Simple UUID generation risks collisions at scale. Regeneration loops add complexity but prevent duplicate tokens compromising security.
The code example in circulation shows standard POST/verify patterns. It works for prototypes. Production systems need:
- Short-lived tokens (15-30 minutes)
- HTTPS enforcement
- Message queues (RabbitMQ, SQS) for async handling
- Mock email servers (MailHog) for testing
DevOps Reality
CI/CD pipelines must test email workflows without spamming users. Monitoring should track bounce rates, delivery failures, and token expiry. SMTP configuration varies by environment—SendGrid for some, self-hosted for others.
Load testing reveals scaling issues before users do. Email services that work fine at 100 requests/hour break at 10,000.
The Pattern
React frontend talks to REST APIs. Email Service handles templates and sending. Validation Service manages tokens. Keep them separate. The architecture supports testing, scaling, and maintenance.
Syntax validation catches typos. Deliverability checks prevent bounces. Token management ensures security. All three matter. Regex solves one-third of the problem.