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

Email Health

One-click domain scorecard — Blacklist, Mail Server, Web Server, and Domain Name System (DNS) checks graded Errors / Warnings / Passed, MXToolbox-style.
Email Records Check

Consolidated Mail Exchange (MX), Sender Policy Framework (SPF), Domain-based Message Authentication, Reporting & Conformance (DMARC), and DomainKeys Identified Mail (DKIM)-selector lookup for an email domain.
SPF Record Checker

Look up and validate a domain's Sender Policy Framework (SPF) Text (TXT) record.
Email Blacklist Check

Resolve a domain's Mail Exchange (MX) hosts to Internet Protocol (IP) addresses and check each against 49 IP blacklists plus the domain itself against 9 domain blacklists.
SMTP Banner Probe

Connect to a Simple Mail Transfer Protocol (SMTP) server, capture its banner + EHLO capabilities, and test STARTTLS.

TLS / SSL Auditing

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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