Email & SMTP Diagnostics
Diagnose email delivery failures at every layer of the stack: verify SPF, DKIM, and DMARC authentication records; probe MX routing and SMTP banners; audit TLS certificates; and check sending IPs and domains against 50+ blocklists. Use them to troubleshoot a specific deliverability problem or run a full pre-send audit of a new domain. For ongoing monitoring with alerting, see Email & Deliverability Monitoring →
Email / SMTP Diagnostics
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Email Health
One-click domain scorecard — Blacklist, Mail Server, Web Server, and DNS checks graded Errors / Warnings / Passed, MXToolbox-style.
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Email Records Check
Consolidated MX, SPF, DMARC, and DKIM-selector lookup for an email domain.
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SPF Record Checker
Look up and validate a domain's SPF (Sender Policy Framework) TXT record.
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Email Blacklist Check
Resolve a domain's MX hosts to IPs and check each against 49 IP blacklists plus the domain itself against 9 domain blacklists.
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SMTP Banner Probe
Connect to an SMTP server, capture its banner + EHLO capabilities, and test STARTTLS.
TLS / SSL Auditing
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TLS Quick Scan
Probe which TLS protocol versions a server accepts and show the cipher each negotiates.
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TLS Deep Scan
Full chain validation, OCSP stapling, SCT count, and per-TLS-version cipher matrix.
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Domain Certificate Audit
Search Certificate Transparency logs for every SSL certificate ever issued to a domain — reveals subdomains, issuers, and historical issuance.
Monitor this automatically
NetTests can run these checks on a schedule, preserve historical results, compare changes over time, and alert you the moment something breaks.
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