verimail.co
A high-throughput email verification service that validates email addresses in real time and in bulk. Uses multi-layered verification including syntax checks, domain validation, MX record lookup, and SMTP handshake verification. Processes millions of emails daily with an API-first architecture.
The Challenge
VeriMail needed to build a high-throughput email verification service capable of processing millions of addresses daily with sub-second response times. Existing verification services suffered from poor accuracy, especially with catch-all domains and temporary email providers, resulting in high false-positive rates that eroded customer trust.
The system had to handle both real-time single-address verification via API and bulk batch processing of lists containing millions of records, while maintaining consistent accuracy rates above 97% across diverse email providers and configurations.
Our Approach
We built the verification engine in Go for maximum concurrency and throughput, implementing a multi-layered validation pipeline: syntax checking, DNS and MX record resolution, SMTP handshake verification, and disposable domain detection. Each layer runs as an independent microservice, allowing horizontal scaling of bottleneck stages.
A React dashboard provides customers with batch upload management, real-time verification status, and detailed analytics. Redis serves as both a caching layer for recently verified addresses and a job queue for batch processing. The entire system runs on AWS with auto-scaling groups that respond to queue depth in real time.
The Solution
Multi-Layer Verification Pipeline
A five-stage verification pipeline checks syntax, DNS records, MX configuration, SMTP server response, and disposable provider databases. Each stage operates independently and can scale horizontally based on demand.
Real-Time & Bulk APIs
A RESTful API for single-address verification with sub-200ms response times, plus a batch processing system that handles files with millions of records. Webhook callbacks notify customers when bulk jobs complete.
Smart Caching & Rate Management
An intelligent caching layer stores verification results with configurable TTLs, reducing redundant checks. Built-in IP rotation and rate limiting across SMTP connections prevents blacklisting while maintaining throughput.
Results
VeriMail surpassed its initial targets, processing over 8 million verifications daily with an average API response time of 140 milliseconds. Verification accuracy consistently exceeds 98%, and the platform has become a trusted provider for email marketing companies, CRM platforms, and lead generation services worldwide.
Technologies Used
“Speed and accuracy were non-negotiable for us, and G1 delivered both. Our verification engine processes millions of emails daily without breaking a sweat. The Go-based architecture they designed scales effortlessly with our growth.”
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