Technical Field Reports
Deep technical dives into the infrastructure of modern email deliverability and verification.
![Catch-All Email Verification: Why Most Verifiers Return "Unknown" and How to Validate Properly [2026]](/images/blog-thumb.webp)
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 Bounce Rate: Acceptable Thresholds, Real Causes, and Domain Reputation Recovery [2026 Outreach Guide]
Acceptable email bounce rate is under 2%, with under 1% the real safe zone. Full breakdown of what kills bounce rate, why legacy verification tools miss 6-9% of bad addresses, and an 8-week domain reputation recovery playbook.
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.