📧 MX Record Lookup

🖧
The selected healthy worker peer will originate this network request.
📧 MX Mode
🔍 Domain Lookup
📝 MX Parser
Format: priority hostname (e.g., "10 mail.example.com")
💡 Examples
Click to test domain:
Click to use template:
📋 Recent Lookups
{{ item.timestamp }}
{{ item.type }}
⏳ Looking up MX records...
Please wait while we lookup the MX records...
🔍 DNS Lookup Results
Domain: {{ results.domain }}
MX Records Found: {{ results.record_count > 0 ? '✅ ' + results.record_count + ' records' : '❌ None' }}
MX Records:
{{ record.priority }} {{ record.exchange }} TTL: {{ record.ttl }}
⚠️ {{ results.error }}
📊 MX Analysis
Records Status: {{ parsed.valid ? '✅ Valid' : '❌ Invalid' }}
Errors:
{{ error }}
Warnings:
{{ warning }}

MX Records ({{ parsed.records.length }})

{{ record.priority }} {{ record.exchange }}
{{ record.valid ? '✅' : '❌' }}
Priority Level:
{{ getPriorityLevel(record.priority).level.toUpperCase() }}
{{ getPriorityLevel(record.priority).description }}
Mail Provider: {{ getMailProvider(record.exchange).name }}
{{ getMailProvider(record.exchange).type }} service
⚠️ {{ warning }}
ℹ️ MX Information

MX Records: Mail Exchanger (MX) records specify the mail servers responsible for accepting email messages on behalf of a domain and their priority order.

Priority Values: Lower numerical values have higher priority. Mail servers attempt delivery to lower priority servers first.

Mail Routing: MX records enable email systems to determine where to deliver messages for any domain name.

⚠️

ℹ️ About MX Record Lookup

MX records are DNS resource records that tell sending mail servers where to deliver email for a domain. Each record contains a preference value and a mail exchanger hostname; lower preference values are tried first. SMTP mail routing is defined by RFC 5321, while DNS message and resource-record behavior comes from RFC 1035.

Use this lookup when configuring Google Workspace, Microsoft 365, Fastmail, Zoho, Mailgun, SendGrid, or a self-hosted mail server. It helps confirm the visible MX priority order, detect missing mail exchange records, spot provider hostnames, and verify that a domain intentionally refuses email with a Null MX record from RFC 7505.

Key Features

MX Record Discovery

  • • DNS MX record retrieval for any domain
  • • Priority-based sorting of mail servers
  • • Mail server hostname validation
  • • TTL and DNS class information
  • • Record count and configuration summary

Configuration Analysis

  • • Priority level assessment and recommendations
  • • Mail provider identification (Google, Microsoft, etc.)
  • • Redundancy and failover analysis
  • • Configuration warnings and optimization tips
  • • Null MX detection (RFC 7505)

MX Priority Levels

Priority 0-10 (Highest)

Usage: Primary mail servers
Purpose: First choice for mail delivery
Examples: Main production servers

Priority 11-50 (Medium)

Usage: Secondary mail servers
Purpose: Backup and load balancing
Examples: Failover servers

Priority 51+ (Lower)

Usage: Lowest priority servers
Purpose: Last resort delivery
Examples: Emergency backup

Common Mail Providers

Cloud Email Services

Google Workspace: aspmx.l.google.com
Microsoft 365: mail.protection.outlook.com
Zoho Mail: mx.zoho.com
Fastmail: in1-smtp.messagingengine.com

Email Service Providers

Mailgun: mxa.mailgun.org
SendGrid: mx.sendgrid.net
Amazon SES: inbound-smtp.region.amazonaws.com
Mailchimp: mx.mandrillapp.com

Technical Standards

  • RFC 5321 (SMTP): defines MX record behavior and priority handling.
  • RFC 1035 (DNS): defines DNS resource records, names, classes, and TTL fields.
  • RFC 7505 (Null MX): null MX records indicate domains that do not accept email.
  • Priority Range: Values from 0-65535, lower values have higher priority
  • Hostname Requirements: Must be valid DNS hostnames (A or AAAA records)
  • Load Balancing: Multiple records with same priority enable round-robin
  • Failover: Higher priority values provide backup mail delivery

Limitations and Security Notes

  • MX records route delivery only; SPF, DKIM, and DMARC are separate controls for sender authentication and anti-spoofing.
  • DNS caches can return old values until TTLs expire, so compare authoritative and recursive answers after a mail-provider migration.
  • A valid MX answer does not prove that SMTP is reachable, accepts the recipient, or has a healthy TLS certificate.
  • This server-side lookup sends the queried domain to the resolver used by Online Cyber Tools.

API Usage Example:

POST /api/tools/network/mx-record-lookup
Content-Type: application/json

{
    "domain": "example.com",
    "action": "lookup"
}
Ready