Pavel Stoletov
CTO at EmailShield leading verification and deliverability engineering. Architected the multi-port SMTP pipeline, domain-grouped catch-all probe system, and self-hosted proxy infrastructure that EmailShield runs in production.
Articles by Pavel
Catch-All Email Verification: Why Most Verifiers Return "Unknown" and How to Validate Properly [2026]
Most email verifiers return "unknown" on 15-30% of B2B lists because catch-all domains accept every SMTP probe with a 250 response. Compare how EmailShield, ZeroBounce and MillionVerifier handle catch-all detection differently.
Cold Email SPF, DKIM and DMARC Setup Guide [2026]
Complete 2026 setup guide for SPF, DKIM, and DMARC on cold email domains. DNS record syntax, the 10-lookup limit, the policy ramp from p=none to p=reject, validation playbook, and the verification step most operators skip.
Email Verification API: Real-Time SMTP Validation for Developers [2026]
How a production email verification API actually works: sub-2-second single validation for signup forms, webhook-driven bulk jobs, live multi-port SMTP handshakes, and Microsoft 365 API-level verification. Based on Q3 2026 EmailShield platform data across 8.19M verified addresses.
Email Verification in Node.js: Real-Time Signup Validation Without False Positives [2026]
DNS-only Node.js email verification libraries pass catch-all and Microsoft 365 addresses as valid, so signup lists still bounce 7%+. Here is how to run real SMTP-handshake email verification in Node.js with EmailShield's API and Node SDK at 99.8% verified accuracy.
How Email Verifiers Work: Real SMTP Verification vs DNS-Only Lookups [Technical Guide 2026]
A technical breakdown of how email verifiers work under the hood. Compare real SMTP handshakes vs DNS-only lookups, see why DNS-only tools cap at 91-94% accuracy, and learn how EmailShield's 4-stage pipeline hits 99.8% verified accuracy.