High-Throughput Email Verification
Custom Rust SMTP engine with sub-second verification processing millions of emails
The Problem
Existing verification services too slow and inaccurate for high-volume use. Email deliverability directly impacts revenue for businesses that rely on email marketing and transactional communication. Bounced emails damage sender reputation, increase costs, and reduce campaign effectiveness. Existing verification services were too slow for high-volume use cases and lacked the accuracy needed for production-grade email hygiene at scale.
Our Approach
We built a custom Rust SMTP engine optimized for high-throughput email verification with sub-second response times. The engine handles the full SMTP handshake — DNS lookup, MX resolution, connection, and mailbox verification — without actually sending an email.
The platform runs on 82 AWS Lambda functions in a fully serverless architecture. It processes millions of verifications with intelligent rate limiting, connection pooling, and retry logic to maximize accuracy while protecting sender reputation. Multi-factor quality scoring classifies each address beyond simple valid/invalid.
Architecture
From bulk ingestion to verified, scored email lists
Bulk Ingestion
High-throughput intake pipeline processes email lists of any size. Deduplication, format validation, and domain extraction happen before verification begins.
Rust SMTP Engine
Custom-built Rust engine handles SMTP verification at scale with sub-second response times. Connection pooling, retry logic, and rate limiting ensure deliverability without triggering spam filters.
Lambda Orchestration
82 Lambda functions manage the verification pipeline — from DNS lookups and MX record resolution through SMTP handshake verification and result aggregation.
Quality Scoring
Multi-factor scoring classifies emails as valid, invalid, risky, or unknown. Catch-all detection, disposable email filtering, and role-based address identification.
Tech Stack
Core Engine
Custom Rust SMTP engine
Compute
AWS Lambda (82 functions)
Languages
Rust, Python, TypeScript
Architecture
Fully serverless on AWS
Performance
Sub-second verification
Scale
Millions of verifications processed
Results
Lambda functions
Custom SMTP engine
Verification speed
Emails verified
Full AWS deployment
Quality scoring