Catalog/INFRASTRUCTURE/email-mx-deliverability
SCAN-ID: EMAIL-MX-DELIVERABILITYREVISION 2026.4
INFRASTRUCTURECVSS 4.3 (LOW)

Email Deliverability & MX Health Scanner

Verify mail server records, reverse DNS (PTR), and blacklist reputation to prevent transactional emails from hitting spam.

Technical Scope & Verification Behavior

Tests MX priority ordering, PTR hostname matching, TLS encryption on mail delivery (STARTTLS), and presence on known spam blacklists (DNSBL).

Automated Inspection Checks (7)
Passive URL parameter fuzzing
Non-destructive boundary tests
Header & cookie flag assertions
Differential latency timing

Proof of Concept (PoC) Vector

Canonical test payload dispatched during security surface audits.

Missing reverse DNS PTR record for outgoing mail IP

Probe Execution Simulator

Watch the probe engine test this signature in an isolated sandbox.

probe-runner (isolated ephemeral container)
Click 'Simulate Check' to watch the headless audit engine test this vector.

Remediation Patch

Reverse DNS PTR Setup

patch.diff (dns)
--- a/handler.dns (Vulnerable)
PTR record missing or pointing to default ISP hostname
+++ b/handler.dns (Remediated)
198.51.100.10.in-addr.arpa. IN PTR mail.example.com.

Configure reverse DNS PTR matching the HELO/EHLO hostname of your outgoing SMTP server to ensure high deliverability.

AI Agent Prompt (Cursor · Claude · Copilot)

Copy and paste into your editor to refactor this issue automatically.

"Set the reverse DNS PTR record with your hosting provider to match your mail server canonical hostname."

Run Isolated Check

Test your public domain specifically for Email Deliverability & MX Health Scanner.

100% passive • No server load

Specification Details

CVSS Score
4.3 / 10.0
Severity Level
LOW
Category
INFRASTRUCTURE
Test Vectors
7 automated
Execution SLA
< 2.5 seconds
False Positive Defense
Strict assertion
Related Standards
#Email#MX#Deliverability#DNS

Run continuous monitoring for Email Deliverability & MX Health Scanner

Audit your site across all 41 vectors automatically on every deploy.

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